Pretreatment Before any product can be finished, For maximum corrosion resistance, the surface must be prepared. In fin- zinc-containing phosphate coatings GENERAL INDUSTRIAL ishing products requiring good corro- are the usual. They’re rinsed with SURFACE COATING sion prevention and particularly chromium-containing acidified water AP-42 where high production rates are and dried in an oven before painting. Section 4.2..2.1 achieved, there is no economical sub- In some systems, it is possible to ob- stitute for adequate metal pretreat- tain adequate cleaning and phosphate Reference Number ment. Simple solvent wiping may be coating in a three-or four-stage 4 adequate, or abrasive blasting, de- washer, while other systems demand greasing or aqueous cleaning and con- five to eight stages to produce the de- version coating may be required, de- sired results. By C. 0. HUTCHINSON* pending upon the application. We can- On objects with surfaces accessible Consultant not delve into the intimate processing to sprays, the product,s normally are details and advantages and disadvan- conveyed through power (spray) tages of each pretreatment method washers. On products with difficult-to- here, but a few comments about the reach but important surfaces, clip most common methods are in order. cleaning and/or phosphatizing may be “Chemical coatings” is the name Thus it is timely to summarize con- Some finishing specialists say that now preferred by many paint. manu- cisely, in one place-the PRODUCTS metal clean enough to paint is clean facturers to describe their coating ma- FINISHING DIRECTORY-all the enough to rust; conversely, if steel terials. The nomenclature change is choices in modern methods of finish- won’t rust readily in humid air, it is indicative of the increasing complexity ing available to you. We’ll make only not clean enough to paint. Phosphate of protective and decorative coating passing reference to methods consid- coatings on steel, and oxide or chro- for modern high-production finishing ered to be obsolescent. Finishing tech- mate coatings on aluminum will pre- installations. niques best able to meet the demands vent the rust, but the idea is valid. Paralleling this change in materials of a production finishing line for metal The most universally used system is a widening choice of methods of ap- and plastic products will receive the for preparing cold rolled or hot rolled plication and cure. Electrocoating. most attention. The principal “right ...... ~ pickled and oiled steel for painting in- Sk Powder coating. Radiation curing. use” of a method and some of the re- volves aqueous spray or dip cleaning, g i One reason for the increasing array lated processes, such as pretreatment rinsing, phosphate coating, and rins- 2 of materials and application methods and stripping, also will be examined. ing. Phosphate coatings may be essen- 2 is that the finisher finds himself faced tially iron or they may be complexed F with a- new set of circumstances *C. 0. HUTCHINSON is a well-known with other metals such as zinc and per- 2 brought on by forces beyond his con- consultant in industrial paint-finishing haps calcium. For aluminum, chro- E trol: energy shortages, EPA air-pollu- methods. His background includes many mate conversion coatings are quite g years in technical capacities for Glidden, tion regulations and OSHA. Plus the popular, as are anodic coatings.6z 8 g latest-TOSCA (Toxic Substances Eagle-Picher and other companies. He is a chemical engineering graduate of the Generally, iron phosphate coatings 4 Control Act). University of Cincinnati and has authored are applied to steel to give light coat- 0 For these reasons the product fin- numerous technical papers. A frequent ing weights-about 10 to 80 milligrams b: isher may find he can no longer use speaker at technical meetings, he has been per square foot. Zinc phosphate coat- z existing equipment economically; or active in the Society of Manufacturing ings on steel are applied at heavier his installation may not be able to Engineers and the Chemical Coaters Asso- coating weights-abdut 150 to 300 mil- cope with ecology, safety and energy ciation. Present consulting activities are FIVE-STAGE washer such as this one ligrams per square foot. Zinc calcium for cleaning and phosphatiring electri- demands. Alternative methods of fin- directed toward aiding users of coating phosphate coatings tend to be still ishing and other materials take on ap- materials in introducing new products and cal control enclosures is the nom in heavier-200 or more mg/sq ft. conueyorized /inishing installations. peal as never before. processes in their plants.

1977 PRODUCTS FINISHING DIRECTORY 4 PRODUCTS FINISHING DIRECTORY 1977 5 % PRETREATMENT.. . , iilcorporat.ed, with or without supple- essarv to remove sand or other mate- eliminate the dry-off CIMX~I Irtb mentaryspr&y, in one or more of the rials from the casting operation. steps. Sand, shot, or grit blasting processes Some cleaning agents and some oils are not able to apply a chemical con- and 4 proce !j tanks dn the steel contribute appreciably to version coat.ing such as iron or zinc the biological oxygen demand (BOD) phosphate and they do not remove oil, of the effluent and overflow water in grease, or carbon deposits or “smut.” addition to their contribution t,o This smut or carbon is loose and if not by simple oil contamination. removed some other process, pro- PROCESS TANKS --- The presence of dissolved metal duces appearance as well as adhesion such as iron, zinc, and chromium in problems, particularly with light col- the effluent from the phosphatizing ors when paint is electrodeposited. and passivating treatments also can Blast,ing does roughen smooth sur- produce problems in complying with faces and removes oxide scale, rust, pollution-control regulations, particu- slag and sand. When done properly on lary when the water is discharged into structural steel or other products, to a surface stream. the proper surface roughness, and Under some conditions, significant when t,he surface is painted promptly, reductions in operating temperatures, several coats of paint can produce ex- and consequent,ly lower energy re- cellent corrosion resistance. quirements, can be achieved and still Vapor degreasing with chlorinated maintain effective cleaning and prepa- solvents of parts to be painted has ration for painting.l been used widely for many years. Re- Mired Metals. In some cases you cent air pollution and OSHA regu- can achieve acceptable results by pre- lations have influenced the types of treating a variety of metal surfaces solvents acceptable as well as the such as steel, zinc, and aluminum in methods of application. Vapor de- the same phosphatizing system; but greasing is capable of removing sol- Diamond Shamrock’s new phosphate normally something less than t.he opti- vent-soluble oils or greases, but leaves (largely due to elimination of the dry- coating system eliminates the oven off oven). And - because most of the mum is obtained on one of the metals the insoluble material on the surfaces and 4 tanks because it’s a solvent. Iron solvent can be reclaimed - it minimizes if several metals are processed in the of the object to be painted. and steel parts are cleaned, rinsed and the pollution problem. The Cool-Phos same solutions. Combinations of vapor and spray phosphatized in a four-step continuous coating protects unpainted parts from sequence in a single tank. They come rusting, for up to a year in storage. To prepare plastics for painting you degreasing may be useful. Phosphate out cool and dry as the solvent must. remove or eliminate mold-re- coatings can be applied by using the evaporates at the end of the sequence Let us send you more details. Fill in the lease compounds such as silicones 01 proper mat,erials. with an excellent bonding surface coupon today and receive the i& paint, rubber or plastic. illustrated brochure on Cool-Phos one- stearates, and dust from machining. tank phosphatizing. Magnesium, terneplate, copper, tin, SUMMARY: PRETREATMENT Compared with the 5tank water-based chromium, or cadmium plate also 0 Iron, zinc, or zinc-calcium phos- iron phosphate system, Cool-Phos typically has operating costs 40% to must be subjected to cleaning and/o1 phate treatments are the most com- 60% lower. Send to: Diamond Shamrock Corporation conversion coated before painting. monly used in finishing steel. Electra Chemicals Division It reduces costs for new equipment 1100 Superior Avenue The cleaning of hot rolled steel and l Three, four, five or more stages in and requires up to 80% less space /n Cleveland, Ohio 44114 some iron castings for high-perform- spray washers or dip tanks are com- your,plant. It also reduces energy Attn. Solvents Department mon in high-production finishing. requirements approximately 90% ance paint coatings normally requires I’d like to know more about Cool-Phos: sand, shot, or grit blasting or pickling l Sand, shot, or grit blasting provide to remove oxide scale that may be em- excellent rust and scale removal for Name large steel products and for some bedded in the surface. In the case of Title Phone castings, such treatment may be nec- castings. Diamond Shamrock Company 6 I'RODUCTSFINISHING DIRECTORY 1977 Address For more dntn circle 305 on Postpaid Card City State-Zir3 5 YKl!i’l‘KWL’I’MJ!iN’l’ . . . prove adhesion characteristics. I . Vapor degreasing with chlorinated solvents‘ removes solvent-soluble l Phosphate, chromate, or oxide (ano- Special Effects Are Possible With Air Spray oil. Some additional treatments dizing) are the most prevalent SYS- may be necessary to remove soils terns for preparing aluminum for Adopted forpublication in the PRODUCTS FINISHING DIRECTOR y painting. not soluble in solvents, and to im- from “How To Apply Speciwl Decorutive Finishes with CL Spray Gun,” by Walter Dany, Binks Mfg. Co., published ori@nally in MUY 1968, PROD- UCTS FINISHING.

How To’Apply Paint in Production The conventional air atomize paint Lacquer mixed with camphor, spray gun offers versatility for devel- atomize hand-spray-guns is their ver- when sprayed and dried, will create a Hand-operated, air-atomizing oping unusual and distinctive finish satility. Many different operating con- frosting or crystalline-type effect. spray. For many years, the use of air- effects. Decorative finishes can be ditions can be accommodated by skill- Wet painted surfaces can have col- atomizing, hand-manipulated paint- obtained by varying the coating mate- ored chips of metal flakes, powders or ful spray persons and careful solvent spray guns to apply paint on a wide va- rial, equipment and/or the operator blending. A wide variety of shapes and pearlescent materials sprayed on the riety of sizes and shapes of parts was technique. surface to add color. the most popular method in the prod- Materials used to obtain special fin- Enamels specially formulated with uct-finishing plant. It best met the ish effects are as follows: a high concentration of metallic par- needs for production of many quality For veiling or cobwebbing, a lac- ticles and sprayed with low air pres- items, particularly in applying attrac- quer or vinyl material is used. When sures will provide clusters of particles tive, glossy finish coats. these materials are thick and sprayed in small blotches to form a ham- Conventional spray painting is still with low air and fluid pressure, they mertone-type finish. Other types of a very appropriate and effective way tend to string out, web and stick to- enamels can be formulated so that for you to apply paint. It is partic- gether, creating a marble or random- during the heat curing of the material, ularly useful if a large number of co101 line effect. the finish will lift and wrinkle. changes are required during a given Thinned lacquers can be used for A texture-type finish is achieved by working day, or if random loading of distressing furniture and picture using a water-base material mixed various sizes and shapes prevents use frames. The same material, slightly with sand-like particles. After spray- of the more efficient electrostatic ap- thicker, can be used to obtain a spat- ing and before drying, the material plicators. Hand spraying is still hard ter effect. can be wiped with a trowel to form to beat if important areas are not ac- Water-borne paints mixed with col- some special pattern. cessible to automatic or electrostatic ored lacquers when sprayed together Antiquing, shading and toning is applicators, too. will produce a multicolor effect on a achieved by spraying the wood and Hand spray often will waste paint in surface-all from the same container. wiping off the excess material before the form of overspray (if 40-60 pet of the paint sprayed lands on parts, that’s considered normal). This over- sizes can be painted to achieve good booth, flash-off areas and curing spray also makes necessary large ail appearance. So it is still difficult to ovens. make-up systems, water-wash spray match the versatility of air-atomize Higher costs with exempt solvents. booths and sludge-reclaiming systems. hand-spray painting. Capital and j&2 cost of after-burn- Labor cost is high in comparison with In conventional (non-electrostatic) ers to reduce solvent emissions. other methods. In some situations, HAND SPRAY still offers great uersatil- spray application of organic-solvent- Fire frn~nrcfs and consequent neces- hand spraying requires use of rela- ity. In this automotive plant it’s being borne coat,ings, there are several limi- sity for explosion-shielded electrical tively large amounts of reducing sol- used in a modern glass-walled spray tations that must be considered care- gear and other isolation equipment. vent, which is evaporated to the at- booth with down-draft ventilation re- fully by today’s product finisher: OLvrspl,ay losses and consequent mosphere, causing air pollution. movingpaint ooerspray into water cur- Air pollution caused by evaporation tain beneath /loor grate. material cost, as well as need for Perhaps the greatest asset of air- of the organic solvents in the spra? equipment, process and maintenance p.. : SPRAY PAINTING . . . SPRAY PAINTING . . . it dries. Material which remains be- equipped with low-pressure fluid low air and low fluid pressures. Pres- about 3 psi (20 kPa) fluid pressure hind will~highlight the wood grains. regulators at each station for finer sures in the O-l 5 psi (0.103 kPa) range and 5 psi (34 kPa) air pressure. Spraying a gold or darker color into control. A second air regulator is re- are generally satisfactory. corners and contours helps to high- quired at the oil and water extractor, In some cases, gravity buckets are For cobwebbing or marbleizing, a light these surface features. at the tap off the main air line supply used. These hang above the spray op- standard, external-mix air nozzle, si- Simulating vinyl is a two- or three- or on a double regulator on the pres- erator’s highest reach. phon or pressure feed will work. step process. A base coat of the sure tank to control the air going into Actually most special effects result (Note: siphon nozzles must be pres- thinned material is first sprayed using the spray gun. from applying material that has not sure fed.) A cobwebbing or marbleiz- standard methods. A second coat is Many equipment suppliers can pro- been fully atomized. Unfortunately, ing material is required and the con- applied, using the vinyl-not thinned vide a small regulating valve which is this is where most problems occur. trol setting is 5 psi (34 kPa) fluid but thick and heavy. Low air pressure connected to the handle of the spray Some spray operators are pos- pressure and 8 psi or 55 kPa air is used so as not to atomize the vinyl gun. This valve will regulate air as sessed with the idea that the only way pressure. into fine particles. In some instances, long as air is moving through the to spray is to use main line pressure, Spatter requires a special external- to ensure a better finish, a fine third spray gun. When you stop spraying, with air and fluid regulators turned all mix air nozzle which has the air jet coat is applied with the same thinned air pressure builds up to main-line the way “on.” They think that the holes drilled off center to cause the air materials as in the first coat. pressure and equalizes in the spray spray gun must “sound right” or have to swirl as it breaks up the material. Equipment. Most special decora- gun. Then when the trigger is pulled, a “recoil.” When this happens, it be- Start at 8 psi (55 kPa) for fluid and 10 tive effects are achieved using pres- a large burst of air rushes out. The comes impossible to achieve special psi (69 kPa) for air. sure-feed equipment. This means that pressure drops until it reaches the decorative effects, and the operator Distressing or flyspecking is very the material is forced through the point where the needle valve was set. may complain that the equipment is This type of arrangement might suf- similar to veiling or spatter. The spray gun. The size of the equipment malfunctioning. equipment and starting pressures to supply the material varies from a fice if time is available to let the pres- There are constant-bleed low-pres- would be the same. small, one-quart pressurized con- sure drop to the regulated point be- sure regulators available which are tainer connected directly to the spray fore the spray operation begins. If the designed to maintain low air and fluid Frosting, hammertone, and wrinkle gun, to a large, five-gallon fluid-pres- material requires higher fluid pres- pressures without being able to go finishes require proper material se- sure tank or material-handling pump sures than air pressure, the valve will above their maximum reading. With- lection more than any special type of with a fluid regulator. It depends upon operate only when placed after the air out accurate and properly maintained equipment. Standard air atomizing production requirements. The control regulator on the spray gun handle. controls, there is little possibility of equipment with agitation and proper that must be present on the pressure The controls needed are basically achieving any kind of standardization spray techniques will permit the appli- cup, tank or pump is an air regulator. the same as for the application of of a particular decorative effect. cation of these finishes with a min- It controls the air pressure entering standard finishing materials with con- imum of problems. the cup, tank or pump. This in turn will ventional equipment. But these con- Veiling requires a special nozzle Application of multicolor finishes control the fluid pressure. Pumps will trols must function accurately. kit, veiling lacquer, and most of all, requires an internal-mix atomizing require a low-pressure fluid regulator. The secret in applying most decora- positive control over air and fluid nozzle; stainless steel fluid nozzle; Pressure tanks also can be tive special-effect finishes is use of pressures. A starting point would be and equal low air and fluid pressures. Spray catalyzed coatings. Be- to remove the atomized paint particles epoxy or urea materials, epoxy polya- ventional spray, for the purpose of from the exhaust air. cause of their ability to cure at lower mide, polyurethane, or other materials lessening air pollution. temperatures, two-component coat- Need for air make-up systems to can be applied as two-component for- In spray-applied water-borne coat- provide filtered, heated air to spray ings are receiving renewed attention in mulations that cure with little or no ing systems for steel, the following booth. Capital investment, fuel and these days of energy shortages. The external heating. may be limiting factors: two components may be premixed or power costs must be considered. Spray water-borne coatings. Steel surface must not rust as a re- Limitations in quantity of paint to they may be sprayed simultaneously With recent emphasis on pollution of suit of application of the water-borne by the same, but special, spray gun. In be stored in a given area, and need for the air by hydrocarbon solvents used coating. either case the two components chem- fire protection. in thinning paint, the product finisher Amount of area to be sprayed and Accessibility to the surfaces to be ically react to cause polymerization has given more consideration to appli- and cure of the coating. Catalyzed the importance of completed film ap- coated. cation of water-borne coatings by con- pearance must be such that there are

12 PRODUCTS FINISHING DIRECTORY 1977 1977 PRODUCTS FINISHING DIRECTORY 13 sr'KAX r'Aln1lnCr... Choose from seven basic Using an internal-mix air nozzle will which can be sprayed on the tops of minimize rebound and produce a bet- cars. It simulates the vinyl texture ter visual pattern definition, as com- sheets which generally are used for Afordson Spray Systems pared to an external-mix air nozzle. this purpose. Antiquing, shading and toning re- Again, any standard piece of exter- Can you reduce coating application costs without sacrificing finish quality? quire accurately controlled standard nal-mix conventional equipment will With seven Nordson systems to choose from, you can select the exact touch-up equipment. The final effect do the trick, provided it is pressure fed equipment needed to meet your budget, line speed, coating specifications, will be a result of the spray operator and low minimum air and fluid pres- safety and ecological requirements. sures are used. technique. Our aim is to provide the equipment that will earn back its cost within Spray Operator. The spray man is Textured finishes are applied by the first year of operation. using equipment that can handle wa- the most important factor in achieving ter-borne, sand-like particle fillers. these finishes. He must be able to We’ll custom-assemble your outfit from standard Nordson components - The equipment must be selected to change his spraying techniques and pumps, heaters, electrostatic power packs, guns, nozzles, withstand corrosion and the abrasion use ingenuity to meet the particular reciprocators, filters, valves, hoses, cables of the particles. Standard external- finish requirements. and accessory fittings. mix nozzles can do the job. But inter- Many of the long-standing rules for What system will you have? All seven nal-mix nozzles will minimize over- spraying must be violated. Distance available for manual or automatic operation. spray rebound and increase applica- from the spray gun to the work will Write to NORDSON CORPORATION, tion speeds if air nozzles’ tip replace- vary. The gun must be farther away in 312 Jackson Street, Amherst, Ohio 44001. ment can be tolerated. some instances. Sometimes it must Phone : 216-988-9411. Also available in Flocking requires a special airspray vary as the spray operation takes Canada, Mexico, Europe, Asia, Australia, For Better Ways to ADD/V gun to handle chipped, flaked or pow- place. Waving or arcing the spray gun South Africa and Japan. Coatings and.Adhes&& dered materials. The air pressure will are usually signs of bad technique, vary depending on the weight of the but in decorating, these “faults” may flock and the amount to be deposited be desirable in order to have uneven Airless Powder on the surface. This type of spray gun amounts of material deposited over Known for its ability to save the surface. Moving the spray gun in material costs by the drastic Electrostatic is most effective when held in an up- reduction of overspray. right attitude. Change in the spray circles and unrelated directions helps Provides thick, glamorous produce a random pattern. finish with excellent corrosion gun attitude either up or down can in- resistance. 95% to 100% crease or decrease the amount of ma- Does this mean that you can select Hot Airless utilization of material. No terial deposited on the wet painted just anyone and let him wave a spray The system that reduces the pollution of air or water. surface. gun about to get a special decorative viscosity of materials and effect on the final finish? Definitely minimizes thinning with Simulated vinyl. A “vinyl-top” ap- solvents. pearance can be provided on au- not! Actually you must be more selec- Air tomobiles by using a special material tive than ever before. The operator Airless Electrostatic no “dry overspray problems.” Adjustments in evaporation rate of Electrostatic for Waterbornes Use of paint heaters and/or high reducers to compensate for applica- Provides wraparound Combines electrostatic efficiency pressure airless atomization not likely tion-condition changes much less characteristic to spray pattern. with benefits of water-base. to be as helpful as with high-solids sol- available than for solvent systems. Improves edge coverage, Nordson systems are safe, efficient, Overspray into water-wash booth, if speed of application and reduce material usage and vent systems. material utilization. maintenance cost. Electrostatic equipment more ex- voluminous, is a bigger problem than pensive and complicated than that for the same amount of solvent paint solvent systems. overspray. Air Electrostatic Continuous Circulating system piping for paint Flash-off zone between application For solvent-based paints. likely to require stainless and thus and heat of oven more critical and Permits spraying of standard Coaters cost more. more difficult to adjust seasonally. materials and many metaltics Hot airless systems for high with superb coverage, volume production. Nonpolluting wraparound, and material high speed finishing.. up to 14 PRODUC’IS FINISHING DIHECTOl~Y utilization. 95% material utilization.

For nore data circle 307 on Postpaid Card L SPRAY PAINTING . . .

must realize what he is doing and spray gun was held close, or far away, know just what effect he is trying to or moved in a special way. achieve. Sample panels which serve The final decorative pattern on the as models for the design pattern must finish is the product of the imagina- be explained to the spray operator. tion of a spray operator and his skill as He must be told when and where the a true craftsman with a spray gun.

SUMMARY: CONVENTIONAL, also helpful in this respect in some in- AIR-ATOMIZE SPRAY stances, and are commonly used with l Is excellent where there are fre- airless spray equipment. quent color changes. Hot airless spray reduces the l Will coat almost any shape or as- amount of overspray dust that con- sortment of sizes. taminates a spray booth or work area. l Will apply catalyzed paint.s, which It also lessens the amount of solvent conserve energy. required and thus the quantity evapo- l Will apply water-borne paints, rated into the atmosphere. Applica- which lessen air pollution. tion problems associated with vari- AUTOMATIC SPRAY. Gun is positioned DRY POWDER can be sprayed through to spray parts passing by on special fix- l Is wasteful of paint in the form of ation in the temperature of the paint overspray: supplied to the spray gun are alle- special spray gun which electrostat- tured conveyor. A high-production way viated. Less compressed air is needed ically charges the powder particles. to paint small, regular objects such as l Requires energy because of high ex- Powder is attracted to grounded sur- the golf balls shown here. haust requirements. in the finishing department. And heav- face-a tubular metal chair frame in be ELECTROCOATING is very popular in l Can be used on automatic spray gun ier films can built without runs or this case-and then powder coated ob- the automotive industry. Here a truck movers to lessen labor costs. sags. Hot airless may produce higher ject is sent to oven. Powder melts on the dives into tank of special paint, where gloss, too. surface, fusing into a continuous coat- paint will be elect&ally attracted to the Airless and hot spray. In using The factors that might be consid- ing in the heated atmosphere. surfaces to prime coat on all surfaces. conventional air-atomize guns, the ered limiting in the use of airless spray, compressed air used to atomize the with or without paint heaters, are as paint often causes sufficient turbu- follows: lence to prevent the proper deposition Dirt, seed skins, and other coarse of the atomized paint particles onto particles can obstruct the flow of paint the surface to be painted. This is par- through the tiny orifice which pro- ticularly true in painting interior sur- vides the volume control and etom- faces of recessed areas. ization in airless spray. Abrasives or Airless spray uses no compressed air large-particle-size pigments must be in atomizing the paint. Instead, the avoided, as they tend to increase the paint flows from an orifice under great size of the orifice and thus allow more pressure and breaks up into a spray as paint to flow, sometimes with poorer it enters the atmosphere. It may be lik- atomization. Paints to be used with ened to a nozzle on a garden hose, airless atomization and with paint which can atomize a liquid just by heaters should be formulated to with- forcing it through the nozzle, under stand the mechanical and thermal pressure. conditions during application and dur- Airless spray guns will atomize ing “down time.” paints and permit application into cor- Somewhat differerzt operator trctin- ners and recessed interior areas with- ing may be required, but is available, out “blow back.” Paint heaters are to achieve the desired results.

16 PHODUCTS FINISHING DIREC1’OII’f 1977 ,I ELECTROSTATIC SPRAY . . . ELECTROSTATIC SPRAY . . . p.

Special guns; hoses, pumps, etc., are In the case of’ bell atomizers, t.he from an appearance, metal protection, required. The expense may offset t.he force moving the atomized particle or economic point of view, it may be reduced compressed air usage. toward the part to be painted is prima- necessary to rotate or index the parts Spray booth? While in some situ- rily electrical. The disk atomizers use in the spray booth, index them be- ations airless spray can be used for both centrifugal and electrical forces tween successive spray booths, or limited paint application in a plant to movethe atomized particles to the hand spray reinforce those areas re- area without a spray booth, produc- object being painted. In some cases, ceiving inadequate coating. You tion painting of fabricated parts would supplementary air currents or altered should have the largest possible area still require a spray booth. electrostatic fields may be used to in- of important surface to be coated at a SUMMARY: AIRLESS AND Huence the movement of the atomized, uniform distance from the applicators. HOT SPRAY electrically charged particles. Safety. Airless electrostatic spray l Airless spray reduces blowback of Airless electrostatic paint applica- applicators use potentials of 70,000 to paint spray from recessed areas. tion also can be accomplished by forc- perhaps 100,000 volts DC. While theit l Paint heaters lessen the quantity of ing paint through a small or&e at current capacity is limited, it is none- solvent required to reduce paint to high pressure, as in conventional air- theless necessary to isolate them from atomizing viscosity. less spray. The electrostatic field is people to avoid discomfort from elec- l Plugging or abrading the orifice of formed in the atomizing head or by trical shock and attraction of paint airless spray guns must be avoided. passing paint through a charged grid. particles. Water-borne paint-supply Electrostatic spray. Many types Both water-borne and solvent- systems must be either electrically in- of electrostatic paint spray equipment borne coatings a’re applied electrostat- sulated from ground and isolated are available. One of the earliest used, ically. Application efficiencies in the from people, or they may involve in- and still quite popular, is the auto- order of 90-95 pet are achievable. termediate reservoirs that are so insu- matic low-air-pressure-atomizing gun, ELECTROSTATIC DISK feeds paint “Wrap around” of the paint occurs, lated and isolated. mounted in a stationary position or on onto whirling disk, which spins it off in making it possible to attract paint to With some paint formulations, it a moving device that makes it possible thin film by centrifugal force. Atomized, the back sides of parts. This helps to may be necessary to use special pre- for the gun to spray long or wide ob- chargedpaintparticles are attracted to provide rapid and adequate film thick- cautions to protect the eyes of persons jects travelling on a conveyor. Such a tubular products-bicycle frames-in ness distribution for many objects. in the area of electrostatic application this plant. gun will handle solvent- or water- Some automatic electrostatic appli- of water-borne coatings, especially borne coatings, but usually it is most Airless electrostatic spray may cation devices allow quick co101 those containing amine solubilizers or efficient with low-viscosity paints. atomize paint by utilizing centrifugal change without having the operators amine soap emulsifiers. The air-atomize electrostatic gun force to cause a thin film of liquid approach the applicators, and with The need for uniform and contin- can be directed at a variety of angles paint to flow over and off the edges of minimal “empty conveyor.” uous loading of conveyor with parts of relative to the surface being coated. spinning disks or bell-shaped at,om- While electrostatic spray painting nearly the same area and contour is And it can be triggered at various posi- izers. Low-viscosity paint flows over offers these advantages, it also re- obvious. Electrostatic guns do not tions during its movement across the the face of the rotating disk or over the quires attention to certain details work well with widely variable target surface being painted, producing ap- inner surface of the spinning bell- which may decide whether it is appli- areas. plication efficiencies of 70-80 pet. shaped device, travelling to the sharp cable to a given product finishing task: More reducing solvent is required Air pollution may be lessened by us- edge under the influence of the cen- Edge buildup. You must pay close than would ordinarily be used for con- ing electrostatic spray. While some- trifugal force. attention in the design and operation ventional spray. what more solvent, is used to reduce a The combination of centrifugal of automatic airless electrostatic sys- Lower air l>elocities are required in gallon of full-body paint to achieve ap- forces and high electrical voltage tems to minimize t.heir tendency to the spray booth to avoid disturbing plication viscosity for electrostatic forces atomizes the paint. The electro- build heavier films of paint around the the electrostaticall>; guided particles, (compared with hand spray), the in- static forces push the paint particles edges of a part or the edges of a cut-out to improve application efficiency. creased application efliciency often re- away from the atomizer and away section. There is need for grenter ejjort to sults in less total solvent used to from each other. The charged particles Coverage of recesses. Coating thick- avoid air-borne dirt. achieve a given dry film thickness on a seek an opposite electrical charge or a ness in recesses or openings is limited. Total capital equipment cost in defined area. grounded conductor. . If uniform film thickness is important some cases is greater than with con-

18 PRODUCTS FINISHING DIRECTORY 1977 1977 PRODLJCTS FINISHING L~lHE(“I’OH1 I!) DIP PAINTING . . . ELECTROSTATIC SPRAY, DIP PAINTING . . .

Dip Painting. Finishing by immers- coated. Filtration helps to eliminate tain solvents that may be evaporated ‘-ventional spray, although in other the unwanted solids. cases this is a stand-off. ing parts into a tank of paint, then per day and per shift. Parts may float off conveyor hangers. If Electrostatic application of water- .draining and drying or baking has been any water is carried into the paint Stripping of hangers in the paint tank on the parts, and if this water .borne coatings also involves some limi- successful for many, many years. It is may cause contamination. carries water-soluble materials, a vari- tations, as listed below: still a good method. Painting of prod- In solvent based, dip-applied paint Isolation of application equipment. ucts involving assembly of a large ety of difficulties may occur. systems, there are several factors that Solvent-solublegrease or oil, certain Hoses for material, the paint supply number of components into a rela- tively large, bulky item, such as re- may decide whether dipping is appro- silicone compounds, or some other in- system and other components must be priate for a given application: separated from people in the area. quired for some farm implements, is a compatible materials can cause film Film thickness will be lower imme- There are a number of innovations good application for dip painting. defects such as craters or run out from Where metal protection is important diately under cut-out or punched-out the space between two pieces of metal that have been reported. openings or holes; thus metal protec- Lower efficiency. Percent of paint and where appearance is not para- where the contaminant was trapped. landing on the target from airless elec- mount, dip coating is often the best tion will vary unless there is some Drip and drain areas represent spray reinforcing of thin areas or un- trostatic equipment is lower with wa- .and most economical method. Many paint loss, fire hazard, and sometimes ter-borne coatings than with solvent- dip systems have been replaced by less slow solvents and/or a fume-la- expensive maintenance. more modern methods which produce den-air drain chamber are involved. Appearance problems. Excessive borne coatings. Sharp edges, particularly top edges, Increased cost of equipment for better appearance and more uniform age, contamination or inadequate fil- electrostatic application of water-‘ coatings, however. will have even less film and metal pro- tration and solvent balance may result b tection than flat, vertical surfaces in “seed” or dirt problems that pro- borne coatings. Some small objects that need coat- near the top. of duce rejects and rework. Application metallic-pigmented ing on only one end are best handled Drain-out holes to prevent puddles by racking and partial dipping: put- A heavy, thick bead may develop coatings may not be possible, even may be necessary to improve paint with electrical isolation. ting a rubbery plastisol coating on along the bottom edge or drip-off economy and dragout, reflow, fume point. It may contain an air bubble Flash-off time after application and only the handle of a pair of shears, for wash, and appearance. before baking may be more critical. which results in a bare area in some as- example. The production of a bead of Reflux. Unless oven air movement, paint on the end of a bobby pin is also sembly and handling operations. part design and hanging are proper, it Air pockets. If the part design and/ SUMMARY: ELECTROSTATIC an example of a good application. is possible to develop fume or solvent Large numbers of small parts that or hanger design and maintenance are SPRAY washing which removes most of the not correct, air may be trapped in the l Electrostatic spray is an efficient need coating for color, appearance or uncured paint film. part while it is immersed, resulting in way to apply paint on metal sur- mild protection, such as drapery hard- Hangers are recoated with each ware, are commonly dip painted. unpainted areas. faces, but it uses more solvent to process cycle. This may interfere with achieve application viscosity. Large, bulky, complex-shaped prod- Paint consumption. All surfaces hanging (in small holes) and require wetted by the paint will consume @ Electrostatic can provide significant ucts such as roof trusses, welded to- expensive stripping. gether from rods and angle iron, are of- paint, even those surfaces not requir- wrap around, will coat sharp edges Fire hazard. Dip tanks filled with ing protection. and can be highly automated. ten dipped in a “shop coat” or primer. Dip painting has a number of draw- solvent paint contain flammable ma- If thick films are required, it may be l Electrostatic spray may apply too terial. Expensive underground storage necessary to dip at rather high solids much paint to an edge, may fail to backs, however: Variation of thickness from top to facilities with quick-dump valves and and viscosity, resulting in slow and in- coat interior and recessed surfaces, fire-extinguishing equipment are often complete drain, fat edges and beads. requires rather uniform conveyor bottom of a part. required. A large volume ofpaint must be on Electrostatic detearing also may be loading of size, shape and area of Jerky conveyor motion may cause necessary. parts for efficient painting. hand compared to usage. It’s messy. There is prolonged drip- uneven appearance and sags. Water-borne dip coating systems for l Electrostatic guns can be installed Variations in the :emperatures of ping from time of removal from paint steel also have some limitations: for quick color change. parts, paint and air in the drain area Steel must be free of oil or grease to to drying. l Some electrostatic systems require can cause variations in film thickness, permit application of a continuous substantially less exhaust and A color change requires an addi- appearance and metal protection. tional tank or dumping of the tank. film. No water break is permissible. make-up air than hand spray for the Solvent pollution. In many states, Any water-paint-soluble materials same painted surface area. The paint is often contaminated by there are limits on the quantity of cer- foreign material on the parts being on the surfaces of the parts must be of

1977 PRODUCTS FINISHING DIRECTORY 21 20 PRODUCTS FINISHING DIRECTORY 1977 DIP PAINTING, FLOW COATING . . .

.such an amount and/or nature as not trol of evaporation of solvent after l Has some of the same problems as terials that deposit on the cathode ’ to exert a negative effect upon the painting, in order to obtain more uni- those encountered in dip coating: from slightly acidic baths have been coated part or upon the coating mate- form coatings. non-uniform naint thickness. dull- develoned. @aI in the tank. Some of the limitations in flow coat- back from sharp edges, fat edges at Elec’trocoating requires more tech- Parts niust not float off hooks or ing with solvent-borne coatings are as the bottom. nical sophistication and competence fish-tail excessively. follows: than most other paint finishing meth- Paint must drain from the part Longer drain area and more flash- Electrocoating. Much has been ods. In some cases it also requires bet- without puddles or pockets and with- off time. are required, with somewhat written and said in the past 15 years ter metal pretreatment and higher en- out excessive refluxingin the interior. more expensive solvents and air pollu- about the electrodeposition of organic ergy input. Capital cost for equipment When the part is immersed, paint tion possibilities. coatings onto conductive surfaces is relatively high. The servicing cost by must be in contact with all surfaces to Enclosure around the drain cham- from aqueous media. Air pollution the paint material supplier is often be pain ted. ber and flash-off zone is normally re- from solvent evaporation is lessened. substantially higher than with the Water sensitivity. The part or as- quired to keep the work clean. Protection of inaccessible metal areas other application methods and there- sembly must not contain materials or Fume washing, thin film at the top is better. Less labor is required. Film fore higher prices for the materials components that are damaged by wa- of the drain, on sharp edges and thickness control and uniformity are may be required. Applications are gen- ter or water paint compositions. around cutouts can be expected. This excellent.‘3-14,15 erally limited to those involving some Any trapped paint between mating will result in reduced metal protection Awareness of energy shortages minimum volume or area per unit surfaces must not run out in the oven or a requirement for touch up. causes more careful study of total to produce unsightly appearance. Larger exhaust air requirements, to electrical energy needs in electrocoat- 2 keep solvent concentration low in ing today. Advances in technology, ; SUMMARY: DIP COATING drain chamber air and thus improve paint formulation and equipment de- 6 l Allows painting of a wide variety of safety. sign are providing materials and sys- 2 sizes and shapes, including inacces- Wedge effect. Major differences in terns that operate at lower voltage, g sible, recessed areas and sub-assem- film thickness, top-to-bottom of long with lower current per square foot per y blies. Variations in material of con- parts, thus excessive paint near the minute and lower chiller demands. 8 struction may be no problem. bottom of the drain pattern. Film thickness distribution from the $ l Care must be exercised in painting Flow coating with water-borne top to the bottom of a part and from enclosures, in order to prevent coatings involves some altogether dif- exterior to interior has been improved, g “fume washing.” ferent limitations: too. And developments in paint formu- ‘? l Large volumes of paint may be re- Foaming tendencies of the paint. lation and manufacturing to improve g quired, producing fire hazards, risks Bubbles, streaks, and film defects performance in ultrafiltration have g of contamination, or high inventory are more common. improved the coatings and reduced costs. Sensitivity to surface contaminants water pollution. l Film thickness variations from the that are either water-soluble or in- Electrocoating is a practical produc- top to the bottom of drain should be compatible with water. tion process for products ranging from expected. Stability of paint is more proble- automobile and truck bodies to light- matical and more than one additive is ing fixture parts. Flow Coating. Flow coating gained needed to maintain solids content. Electrocoating usually involves de- in popularity in the years following position on the anode, from a slightly World War II. It overcomes some of SUMMARY: FLOW COATING alkaline bath. But more recently ma- the limitations of dipping. The volume l Involves less paint than dip coating. of paint in process is much less, fewer l Produces excellent coverage. ELECTRODEPOSITION of paint takes parts fall off the conveyor in applica- l Involves comparatively little labor. place in this large tank filled with spe- tion zones, and some parts that would 0 Solvent evaporation control is very cial water-borne paint. As parts moue float in a dip tank can be coated. important. through the tank,paint is “plated”onto Flow coating with solvent-borne l Offers less risk of parts floating off the part-usually requiring about one coatings usually requires careful con- the hooks. minute to deposit one mil.

22 PRODUCTS FINISHING DIRECTORY 1977 PRODUCTS FINISHING DIRECTORY 23 ELECTROCOATING, COIL COATING.. .

time; such as perhaps l,OOO,OOO square Roller Coating. Coatings may be feet.(92;903 sq m) at one mil(O.039 pm) rolled onto flat surfaces by resilient per month. rollers coated with paint. When these Electrocoating has some limitations rollers travel in the same direction and FABRICATED METAL PARTS can be and they need to be met squarely in at the same speed as the surface to be coated efficiently by dipping into special the decision-making process: coated the process is called direct paint which is electrically attracted to , Electrocoating is a sophisticated, roller coating. When they rotate in a all surfaces. There are no runs or drips, technically complicated process for direction counter to the movement of even though this is a dippingprocess. large-scale production operations. But the surface the process is reverse roller when properly designed, installed and coating. controlled, it can be operated by con- When applied to metal sheets scientious, intelligent people with lim- (rather than continuous coils) by ited formal scientific training. smooth rollers or by rollers with in- Somewhat higher capital inuest- dentations and projections to produce ment and energy-operating costs are art work or printing, direct roller coat- involved when one compares electro- ing is called metal decorating. coating and other coating methods. When direct or reverse roller coat- Pollution problems. While air pollu- ing is applied to a continuous strip of tion is greatly reduced with electro- metal, it is called coil coating. coating, in comparison with several Application efficiencies approach other methods of paint application, it 100 pet. Color can be changed without can cause water-pollution unless care- stopping the line by mechanically re- fully designed, installed, and con- moving one roller from contact with trolled. Plants that are discharging the surface and moving a second coat- effluents into surface waters must be ing roller with a different color into particularly careful. contact with the surface to be coated. The, number ofpotential suppliers of Roller coating also can apply accent paint for electrocoating is reduced colors to raised lettering or it can ap- from perhaps 1000 to 100 or less. ply fillers on some porous surfaces. Metal pretreatment and cleaning Major quantities of paint are rolled are more critical for electrocoating onto such ‘products as roof decking, than for application of solvent-borne siding and metal coils for other miscel- coatings. laneous uses. The container and sign industries are also large consumers. The volumes of material used in roller coating are probably second only to SUMMARY: ELECTROCOAT the volumes of spray-applied coatings l Practically eliminates air pollution, for the automotive industry. and if properly designed, will not in- Coil coating requires major capital crease water pollution. investment and high volume produc- Photo: DeVilbiss Co l Fire hazard from solvent is almost tion to achieve economical operation. ELECTROSTATIC guns on a reciproca- eliminated, but some controllable tor automatically spray items moving Limitations in the practical use of by on conveyor. electrical hazard is introduced. roller coating include: l More uniform and complete, contin- l While roller coating has been used PROGRAMMABLE ROBOT can dupli- uous coverage of external and inter- for applying graining ink on metal nal surfaces can be achieved. cate the motions of a spray man. This and comuosition board for obiects robot is fitted with low-voltage electro- such as-television cabinets “and static spray gun.

24 PRODUCTS FINISHING DIRECTORY 1977 j Table A COIL COATING, POWDER COATING.. . Ip;;

Comparison of liquid Paint Appliiioo Yothcds other furniture items and has had the coating enclosure. Air is blown I some applications in the appliance into a chamber under the porous plate, 11 b 11 pip 11 Conrentional 11 Electrostatic Electrocoat industry, it has not gained much ac- causing the powder to be “fluffed up” , cat Spray War ceptance as a finishing method on or fluidized. Parts can then be dipped Water or Solvent WlS WlS WlSlS 111 IS s P other fabricated objects. into the “fluidized” powder in much Regubr or High Solids I I [R(HS z R HS be I. ^I.. n,n 1 I the same manner as would possible with a fluid. SUMMARY: ROLLER COATING By controlling the air pressure, the An efficient, high-speed, widely used porosity of the plate, the amount and method of applying very uniform, qualities of the powder on the top side - high-quality liquid coatings on flat q,” ,, Y ,.a, - ,, 1 A A of the plate, the temperature of the surfaces such as coil, strap, tape, and part entering the fluidized bed, and the Dj D 11 1 ( 11 panel products. ,, * I n I n II n n 1 A mass and geometry of the parts, prac- tical coatings are achieved. Powder Coating. The first refer- Electrostatic Fluidized Bed. The es- ence to powder coating appears to be a sential components described in fluid- British. - Patent issued to Shori Metal- ized bed coating are also used in elec- hzmg Process, Ltd. in 195O.l” I7 In trostatlc fiuidized beds, with one 1952, the fluidized bed process was de- principal addition: a charging elec- veloped in Germany.lY In December, 1955, the fluidized bed process was dis- FLUIDIZED BED aerates a tank ofpow- played for the first time in the U.S. by dered resin to give it fluid-like charac- Polymer Corp. at the National Chem- teristics. When heated object is dipped ical Show in Philade1phia.l” By 1965, into the dry powder, particles melt and A = Advantage W S = Soluent-borne ..- ~” = Water-borne D = Disadvantage I or perhaps earlier, the fluidized bed fuse on surface, coating the object. HS = High Sohds Blank = Intermediate between Aand D 1 R = Regular Solids i = Powder process had gained practical produc- tion applications in the appliance in- FLAT PARTS can be coated efficiently uously flows from a special head in a using a curtain coater like the one thin “curtain” as flat surfaces move be- dustry.Z” Twenty-two suppliers of shown here. Coating material contin- neath. Surface is coated only on the top. powder coating materials were listed in the 1971 PRODUCTS FINISHING DIRECTORY. In 1975,40 powder ma- terial suppliers and 14 powder systems engineering and installation suppliers were listed. The Second North Ameri- can Conference on Powder Coating was held in Toronto in March 1972 and SME held two Powder Coat.ing Semi- nars, one in 1972, the other in 1973.‘” E Both the SME Conference and the Ca- 2 nadian Seminar were repeated in 1976. z Fluidized Bed. In fluidized-bed pow- “, der coating, parts to be painted are g heated to a temperature above the g melt temperature of the powder to be c used and then conveyed into the fluid : bed chamber. The powder is on a 5 porous plate forming the bottom of 6

1977 PRODUCTS FINISHING DIRECTORY “7 POWDER COATING . . . POWDER COATING . . .

on uncoated or only slightly coated Almost any plastic resin can be ap- and exact duplication of a sprayable areas of the parts to be coated. WOW A plied as a coating by powder coating liquid coating are requirements, these DC power source, dry compressed air, techniques, since there are no require- may be difficult. to achieve with pow- a spray enclosure, a powder-recovery ments for compatibility with solvents der coating. system, and a powder-feed system are and other components of liquid coat- Need for new equipment. Powder required. Parts with dry powder ad- ing formulations. Thus polyethylene, coating cannot be performed with $ hering travel into an oven, where the polypropylene and nylon can be ap- existing equipment. A fair-size capital J powder melts, fuses and cures, if it is a plied easily. investment is required-a new booth z thermosetting material. Powder coating makes possible re- and new guns and powder-handling E Automatic Electrostatic Powder claim of overspray, improving overall apparatus at a minimum, .nlus new c Spray. The mechanism of automatic materials utilization. In so doing, the ovens and washers or a complete sys- 6 electrostatic spray of powder coatings technique eliminates some messy dem in other cases. L)O the1s same as that for manual electro- cleanup tasks that may be associated Safety hazards. Powder can be han- Q) static spray, except that multiple guns with maintenance of water-wash dled very safely. But the user must be g automatically spray from one or both spray booths, for example. aware that it is necessary to keep pow- m5 sides of the grounded object travelling Electrostatic powder coating is self- der-air ratios within the proper ranges 0 through a special enclosure. No oper- limiting, meaning that the charged to avoid setting up explosive situ- g ator is required to be in the booth with powder particles cover conductive ations. And of course sparking must be E the dust-like cloud of charged powder areas until they are insulated by the avoided in powder-application areas. coating material. Much less move- powder, then seek out uncoated areas, POWDER COATING can be done with ment of the spray guns is necessary in effect. This helps to provide uniform automatic guns, as shown. They are than would be required for automatic and complete coverage of an object. SUMMARY: POWDER As we have seen, each finishing mounted on reciprocators which oscil- electrostatic spray of liquid coatings. COATING late guns up and down as parts pass. Powder coating has advantages in method also has its own limitations. Charged powder is attracted to parts - lessening air pollution. Since no sol- This is true of powder coating, too. l Fluid beds provide heavy films with fluorescent fixtures in this case. vents are used for dilution, none are Here are some drawbacks: good efficiency. evaporated to the atmosphere. In cur- Color change. The switch from one l Electrostatic fluid beds eliminate trode immersed in the powder coating ing there are small emissions of or- color of powder to another has been difficult in high-production situations. the need for preheating parts and bed or positioned below the porous ganic volatiles, but not in quantities make possible thinner, more uni- Technology is improving in this area, plate in order to ionize the air which anywhere near those emitted in curing form films. liquid coatings. however, with new powder coating fluidizes the powder. This electrode is . Electrostatic spraying of powder attached to a variable direct-current Powder coating also lessens the tunnels and reclaim systems making amount of makeup air required, since color change more practical for certain provides a way to coat a larger ob- source capable of producing about ject with thinner films. 80,000 volts. The powder particles are there is no need for copious quantities applications. charged. These charged particles repel of exhaust air to be taken from spray Application of thin films. It has been l A wide variety of plastic resins may each other and form a “cloud” over the areas. Lower air exhaust rates may be difficult to achieve thin films-say one be applied as coatings by use of pow- bed. The charged particles are at- satisfactory for bake ovens, too. Both mil or less-reproducibly in high-pro- der coating techniques. tracted to the grounded object and of these factors lessen energy require- duction situations. To achieve eco- l Powder coating will not always du- particularly to bare or uncoated areas. ments, although there may be other nomic benefits it is necessary to lower plicate the appearance of a coating Munual Electrostatic Powder needs for energy inherent in the proc- the film thickness and thus the con- applied by liquid coating methods, Spray. There are a number of hand- ess and these may fully or partially sumption of powder. cannot provide for rapid color held electrostatic powder application offset these gains. Duplicating appearance. Powder change as easily as with liquid coat- guns that will blow a cloud of charged There are definite advantages for coating produces attractive coatings ing methods, and does require new powder particles in the direction of powder coating when a comparatively and many colors are available; but investment in equipment. grounded parts travelling by on a con- thick coating is desirable. Powder there is more tendency toward orange l Powder coating greatly lessens air veyor. The dry powder adheres to the coatings produce this in one pass, with peel and some metallics are difficult or pollution. metal surface and deposition proceeds minimal danger of sagging and runs. impossible to duplicate. So if high gloss

1977 28 PRODUCTS FINISHING DIRECTORY 1977 PRODUCTS FINISHING DIRECTORY 29

.- PRETREATMENT WASHERS, DRYOFF OVENS.. , Systems exhaust blowers to remove the less chemicals in use in the system and Finishing steam from the manufacturing area more exhaust air and steam. and prevent condensation and drip- Dryoff ovens. Parts usually must Dip and Spray Washers. Hot and to headers and risers on which the ping on the parts to be painted. be dry before painting or powder coat- cold rolled steel parts as well as sub-as- nozzles are located. l In some of the most modern systems ing. Normally an oven evaporates t,he semblies fabricated for painting can be l Temperature and pressure gauges in ultrafiltration separates oil from water left as parts emerge from pre- expected to have a number of soils on the header and a throttling valve cleaner solutions to extend the life treatment stages. Sometimes water of their surfaces. As noted previously, between the pump and header pres- of the cleaning solution and reduce hydration is driven off from zinc phos- these soils should be removed before sure gauge. In some systems, these the oil content of the effluent water phate coatings by use of heat, in order painting, and a phosphate coating of- pipes are totally within the chamber to drain. to achieve maximum corrosion resist- ten is applied to improve adhesion as or tank, while in others the principal In dip immersion cleaning and ance. In the interest of conserving en- well as corrosion resistance. header is outside the enclosure. phosphatizing, the parts to be painted ergy, the technology in finishing with- Hot-rolled pickled and oiled and l A storage tank of suitable volume, are moved from tank to tank, remain- out dryoff ovens is making much hot-rolled shot blasted steel can be ex- possibly large enough to hold two to ing immersed for the prescribed time. progress, however. pected to have significant amounts of five times the volume of water Heating coils or tubes, chemical-con- A dryoff oven is normally a short a black or dark gray, dusty or oily sur- pumped per minute. centration-sensing devices and chem- distance from the last station of a face contaminant, normally called l A heater for the solution. Often it ical addition pumps, overflow weirs, oil pretreatment section. Sometimes too smut. The latter may require mechan- consists of a series of tubes into and water separators, exhausting fans little distance is allowed. If most of the ical action such as scrubbing or spray which gas is burned. Heat is then and duct work are often parts of such water drains off rather than having to impingement for proper removal. transferred through the sidewalls of systems. be evaporated with heat and air mo- Vapor degreased steel also may have the tubes to the solution. The tubes Pretreatment: Immersion Versus tion, energy can be saved. Sometimes a gray or black powder-like deposit left are vented to the outdoors, some- Spray. Which is better? Immersion almost complete air drying without on its surface. This is also called smut. times passing through a dryoff oven pretreatment or spray? It depends heat is possible. It normally consists of residues that to gain a secondary use of heat in upon the application and its particular Normally, a dryoff oven in a paint are not solvent soluble. Sometimes it the exhaust gases. In other cases, requirements. system will consist of an enclosure al- includes the soaps in greases used on steam coils will provide heat for the In many situations, dip cleaning re- the parts for drawing operations. solutions. quires larger tanks, more chemicals in Cleaning and phosphatizing solu- l A temperature controller or regu- process, higher floor weight loading, tions are usually sprayed on the parts lator allows the temperature to be more floor space, less electrical power or the parts may be dipped in a series set at some predetermined level. input and less heat. of these solutions. Sometimes combi- l Chemical-concentration-sensing de- In cleaning inaccessible areas, im- nations of dip and spray are required. vices may be used to activate feed mersion cleaning has big advantages. Most common equipment, however, is pumps in order to maintain the With some sizes and shapes, dip the multiple-stage spray washer. It chemical concentration desired. rinsing after dip cleaning or dip consists of- l Overflow weir and drain connec- phosphatizing is the best way. It may * A spray chamber with pipes and tions for overflowing rinses. require much more water to achieve nozzles and an enclosure to keep the l Screen and baffle arrangements to the same degree of rinse cleanliness spray solutions inside. prevent small objects from entering that would be achieved by spray rin- sing accessible surfaces, however. l A water-tight floor, sloped to drain the suction side of the pump. into a tank. l Skimmers built into the tank or as In many cases, spray cleaning and phosphatizing will involve less floor l In some cases, a shield around the auxiliary appendages external to conveyor to keep the chemicals off the tank to separate floating oil and space, less floor loading, smaller tanks, the conveyor. grease from the solution. shorter process time, shorter start up l A pump, usually centrifugal, with l Filters or decanting tanks to remove time, more electrical and gas energy, impeller and housing below water the sludge developed in phosphate level, delivering a prescribed num- coating stages. DRYOFF OVENevaporates water left by ber of gallons of solution per minute l Entrance and exit vestibules with pretreatment beforepainting.

1977 30 PRODUCTS FINISHING DIRECTORY 1977 PRODUCTS FINISHING DIRECTORY 31 DRYOFF OVENS, SPRAY BOOTHS.. . lowing four to seven minutes heating terns may be smaller in these cases. tinie. Overspray from automatic electro- A recirculating air blower may be in- static sprayers may be collected pri- stalled, along with an exhaust blower marily on the interior walls of the cir- at each end to prevent heat spill-out cular booth rather than on filters or into the work area. Some ovens are baffles. The overspray will also collect built with entrance and exit at the on any other grounded object which it bottom rather than at the ends, thus can contact and therefore monorail, achieving a gravity-type air seal. chain, trolleys, etc., are shielded as Sometimes a gas burner distributes much as possible and electrostatic ap- heat throughout the oven and flame is plicators are kept as far as practicable “visible” to the parts being dried. Or from them. tubes carrying the exhaust gases from Water wash booths. In situations the power washer or paint-bake oven where the volume of overspray is rela- tively high, or where it is important to may be used to heat the parts. CONVENTIONAL automatic spray guns A temperature-indicating and con- avoid blowing overspray particles into spray cemmic coating on rotatingpanu trolling device is conventional. the atmosphere through the exhaust for Wearever Corpomtion. Spray Booths. Spray booths are in- from the booth, or where there are eco- nomic advantages in reclaiming the stalled in painting systems primarily COIL COAT line has equipment neces- to confine the overspray. In some cases overspray for sale or re-use, water sary to unreel metal coil, clean and re- they also provide a way of reclaiming wash spray booths have found wide ac- treat, roll on paint, heat-cure the coat- all or part of the overspray. ceptance. For manual operations, they ing, cool and re-reel, all in a continuous, There are four well-established require the same linear air velocity high-speed process. This line is 470 ft types of booths, each with several de- past the sprayer as required of other (143 m) long. sign variations to accommodate spe- booths. cific conditions. The bottom, top, back and two ends .&_... -- -- - Photo: Ross/Waldron Dry booths. When used with manual of most water wash booths are en- spray, dry booths are usually enclosed closed. There may be an open face in on top, bottom, back and two sides. Air which the sprayer works, or a closed is exhausted from the back of the face with dry filters in back of the booth after passing through disposable sprayer. In the latter design, air trav- air filters or around a series of stag- els through the filters from behind the gered plates intended to catch most of operator. A filter reduces the dirt and the paint overspray. Exhaust rates are lint entering the booth and inhibits high enough to draw overspray paint the access of personnel to the spray away from the operator. area. In some disk-type electrostatic Lights are necessary in the closed spray applications, the booth is a cir- booth and are used in most manual cular enclosure around a loop in the booths as well. Fluorescent lights are conveyor, with only about 60-90 de- common, as are lights in the wall con- grees of the circle open to provide an taining the air filters for the air supply. entrance and exit for the parts to be The water pan or reservoir may be painted. Since these booths are auto- above or below the floor of the booth. matic and do not involve a spray man A water curtain often runs down the in the booth, linear air velocities for surface of the booth facing the the much smaller area of open face are sprayer. An overflow water trough or much lower. Thus air make-up sys- gutter at the top of the water curtain

32 PRODUCTS FINISHING DIRECTORY 1977 5* _’ SPRAY BOOTHS, AIR MAKEUP . . . AIR MAKEUP, PAINT BAKING OVENS. . . / of the plant. and an open space above the water Often there is a device for blending inside the oven, visible to the parts the reclaimed powder with fresh, new The air make-up system may con- being baked, or it may be in a combus- ~level in the water pan and below the tain the following: metal surface over which the water material. A small fluidized bed may tion chamber external to the oven. 9 prepare the powder for transport l A blower to draw the proper quan- curtain flows will normally constitute These ovens have a recirculating through hoses to the spray guns. tity of air through the system and blower to take air from the oven, push what is seen in the booth. Down-draft into the room. water wash booths suck overspray A source of direct current provides it through the burner box through voltage for the electrodes in the elec- l A gas burner or other heat source to ducts, ports or openings to all places in through metal grating and into water heat air to a temperature comfort- flowing below. trostatic spray guns. the oven where heat must be supplied.. A pump recirculates water from the Oil-Wash Spray Booths. Binks able for the workmen, particularly The suction side of the blower may be the sprayers. water pan to water the trough feeding Manufacturing Company manufac- connected by duct work to an opening tures a spray booth that uses a special l Filters to remove particulate matter in the wall of the oven or to duct work the curtain and in some cases to one or from the intake air. At one time more sets of nozzles that spray water oil in place of chemically treated water to collect cold air from various loca- in a wet booth. It is claimed by the these were usually continuous, mov- tions in the oven. in the air flow zone below or in back of ing, oil-coated screen filters. Elec- the water curtain. Baffles or elimi- manufacturer that this booth elimi- These ovens will also have a blower nates regular filter changing (as in dry trostatic paper-type filters or dispos- to remove fumes from appropriate lo- nator plates may be installed in the ex- able glass fiber filters are also used. haust air stream after the spray noz- booths), cleaning down time, corrosion cations and exhaust them to the out- of the booth by the water, pollution of l Humidifiers. In some systems, steam doors. Sometimes the suction side of zles and before the blower. or water is released into the air sup- Through adjustments in the chem- water from spray booth cleaning-all the blower is simply connected to an icals used in the water in the booth, with lower power input. The oil is re- ply stream to increase the relative opening in the wall of the oven; in used. humidity of the air to improve other cases the suction side is con- the overspray trapped by the water worker comfort or to reduce the can be caused to float or sink in the Air Make-Up Systems. Paint-fin- nected to exhaust-collecting ducts in ishing systems are often in a room or in ease with which dirt particles pick the oven. The exhaust-collecting duct water pan. The floating sludge may be up static charges. collected, washed, homogenized, a walled-off area of the plant. Power may be located in such a way as to try l Duct work to channel the air from dewatered, and blended with original washers, dryoff ovens, spray .booths to collect most of the water, smoke or material to produce a reclaimed blend and ovens each exhaust some air m or- the heater, blower or filter to the solvent vapor given off by the coatings der to carry fumes, vapors and heat specific locations in which the air is during heating, drying and converting equal to ,the original material when needed. large volumes of paint overspray are outside the working area. Obviously the liquid coating material to a solid. Baking and Curing Ovens. available for reclaim. this air must be replaced. Many These ovens are equipped with a va- Many liquid-paint-application sys- chemical coatings are applied as liq- Powder Coating Booths. The pow- riety of control and safety devices such tems are sensitive to dirt, lint, fiber, or uids and converted to solid films as: der coating booth must be part of a through application of energy such as powder system. The typical powder foreign material suspended in the air l A thermostat to control tempera- in the rest of the factory. If high qual- heat, ultraviolet light, or very high-ve- ture in the oven. coating booth has a dry wall, usually locity particles in radiation curing. metallic, with steep sloping bottom to ity, dirt-free films are required, this l A purge timer to require the oper- factory air-borne dirt must be kept out Coatings requiring heat to cure are ation of the exhaust blower and re- collect the bulk of the powder over- referred to as thermosetting. Those spray. An exhaust system removes the of the finishing room. circulating blower for a predeter- Air make-up systems are designed to that dry by evaporation of water or mined period of time before lighting suspended powder from the air. solvent are referred to as thermoplas- A cyclone is often the first-stage sep- supply slightly more air to the finish- the burners, to ensure that there is ing room than is required for the ex- tic or air-dry coatings. no gas built up in places where an arator. It is a centrifugal chamber that Ovens supply the right quantity of forces the heavier powder to the outer haust needs. This is sometimes re- explosion would result. ferred to as pressurizing the room. energy to produce uniform curing of walls and the air to the center top exit. l A maximum-temperature thermo- The static pressure increase is not the film. They also provide the energy stat that will shut off the gas if the The powder is discharged through the to evaporate the organic solvent or bottom center opening, in a cone- measureable but the air motion at temperature exceeds some specific openings in the wall surrounding the water required to dry the film. level. shaped bottom. Direct-Gas-Fired Ovens. Direct- A bag-type filter has been the con- room is detectable. The objective is to l An indicating, recording and con- replenish the exhausted air with clean, gas-fired ovens allow the products of trolling device, which is for oven ventional equipment for removing combustion to come in direct contact smaller suspended particles that pass heated air and pressurize enough to temperature. with the paint film. The burner may be through the centrifugal separator. prevent entry of air from other areas Indirect-Fired Ovens. If fuel oil is to

1977 1977 PRODUCTS FINISHING DIRECTORY 34 PRODUCTS FINISHING DIRECTORY 35 PAINT-BAKING OVENS, RADIATION CURE . . . be burned as a source of heat for paint banks of heat lamps are erected or SUS- baking, the products of combustion of pended in a wide variety of ways. They the oil usually must not come in cori- often can be moved from one tempo- tact-with the paint coating being rary location to another with relative baked. The color of the paint may be ease. Where gas is unavailable, or lon- darkened or made more yellow by the gevity of production in a given loca- products of partial combustion of the tion is questionable, or where mini- oil. In some cases the products of par- mum cure times are required, these tial combustion produce a smoke or units have much appeal. hazeon the surface of the cured paint. Electric-Heated Ovens. These ovens Therefore, the oil is burned inside are similar to indirect-oil-fired ovens heat exchanger tubes and the air from except that the heat source for the re- the oven is circulated over the outside circulated air is an electric resistance surfaces of the tubes and back to the heater. They are being used where gas baking oven. This reduces the heat is no longer available or where gas is transfer efficiency from the fuel source interruptible. to oven air and limits the maximum Steam-Heated Ovens. In some oven temperature to a practical level plants super heated steam is used be- of about 280F (138C). The balance of cause it is available in sufficient quan- the indirect-fired oven is very much tity, at high enough temperature, and like the direct-fired oven. at economical costs. Steam also may Direct-Oil-Fired Ovens. In some be useful in situations where gas is not rather recent developments and re- available. These then become ovens finements, it has been found possible like the indirect-oil-fired ovens de- Border to Border UCoast to Coast to burn certain fuel oils in certain scribed previously. burners in a direct fired oven to bake a Induction-Heated Ouens. In some range of colors without discoloration specialized situations such as wire Complete Finishing Systems Keeping the country’s metal finishing industry progressing forward is a big or soot accumulation.‘” coating, it is possible to use high-fre- responsibility. It’s one that calls upon experience in designing, engineering, Electric Infrared Ovens. These quency, alternating-current induction ovens heat a variety of specially de- heating of the object to be baked to fabricating and installing quality equipment. achieve satisfactory baking of the liq- signed resistance elements to produce KOCH EXPERIENCE WORKS FOR YOU IN- infrared radiation. The radiant heat- uid coatings. SURFACE PREPARATION Radiation Curing. The develop- CURTAIN COATERS FLOW COATERS ers are often mounted close to the Aqueous products being baked. Some involve ment of high-intensity ultraviolet ELECTROCOATING ELECTROSTATIC SPRAY Non Aqueous DIP COATING recirculated air. All require some ex- light sources, high-intensity electron- SPRAY BOOTHS Powder CONVEYORS OVENS haust air. The effectiveness depends, beam curing apparatus and resins that Wet Wicket Dry react to these energy sources has re- Dry to a considerable degree, on rapid rise Monorail Bake Backdraft in temperature, baking for short times sulted in the introduction of both of Belt Cure Downdraft at relatively high surface temperature these systems to practical production Pallet AIR MAKE-UP and the availability of a paint coating operations. Instead of using heat to that will cure adequately at the vari- initiate polymerization, radiation cur- ations in film temperature occasioned ing depends upon use of monomers by the variations in mass and distance that are sensitive to these forms of Phone, of the surface from the heat source. radiation. Polymerization is initiated wire Some electric infrared ovens have by the electron beam or UV source or write very lightweight heat lamps, and re- rather than by heat. for File flectors assembled in banks. These Much lower temperatures of the GPF-77D For more data circle SO8 on Postpaid Card 36 PRODUCTS FINISHING DIRECTORY 1977 PRODUCTS FINISHING DIRECTORY 37 CONVEYORS.. . AFTERBURNERS, CURING.. . is the overhead monorail, chain and may be equipped with “shear pins” to l Hot air moving at high velocities parts being baked and shorter baking pulley conveyor. It can be arranged to stop the force exerted on the chain at times are involved in their use. Be- and directed at the surfaces of coat- go up and down inclines and make hor- ings being cured. prescribed loads and thus prevent me- cause of their rapid cure, i.e., fract,ions izontal changes in direction. It con- chanical damage. of a second to a f.ew seconds, the coat- In coil coat lines with horizontal sists of the following, with or without ovens, air moving at thousands of feet 6. Slack take-up device, to prevent ing materials must be substantially some of the optional features: loose chain accumulation, usually just free from volatile material and not per minute can also help support the 1. An I-beam, varying in size de- weight of the long catenary curve after the drive mechanism. This is typ- prevent the penetration of the energy pending on the load it must carry and ically a spring or weight and pulley, on deep enough in the film to cure the en- formed by the coil passing through the the size of the pulleys. This I-beam is oven. a U-turn on the conveyor. The weight tire film. continuously welded together except or spring mechanism increases the Radiation curing involves safety for expansion or switching joints. length of the “U” when the tension is and health hazards that can be con- Shapes other than I-beams are also high. When properly designed, in- trolled but are less obvious to the aver- SUMMARY: PAINT used in some cases. BAKING OVENS stalled and adjusted, the “take-up” age factory worker. 2. A continuous-link chain, varying greatly reduces jerking of the chain, l May use gas, fuel oil, electricity, Afterburners. While afterburners, in size depending on the amount of when compared with units without fume incinerators or catalytic con- steam, infrared or ultraviolet, or tension required to pull the weight of electron beams as the sources of en- slack take-up devices. verters used in the painting industry parts through the system and up in- 7. A chain cleaner is used on many are not ovens, they are appendages re- ergy to evaporate solvents and/or clines, etc. cure coatings. lines to remove dirt and scale from the ceiving considerable attention with di- 3. Pulleys and brackets to hold the chain by means of rotating wire rect-gas-fired paint baking ovens. l Baking times are typically 15-45 min pulleys on the I-beam, attach to the with direct- and indirect-fired and brushes with or without air blow-off. They burn the solvent evaporated chain to position the work and extend 8. A pulley lubricator, either an au- from paint films in ovens. The resul- electric or steam ovens; three sec- downward to allow attachment or onds to five minutes with electric tomatic spray device or some other tant heat may be used as an added hanging of the products to be finished mechanism to apply grease to a fitting heat source and in some circumstances and radiant gas heat sources; only a or the work holders to support the fraction of a second with an elec- on each pulley, on a prescribed lubri- it can reduce the amount of gas needed products to be finished. The pulleys cating schedule. for baking and drying. tron beam, and a few seconds with may be spaced at a wide variety of dis- ultraviolet. 9. Roller turns are sometimes used, High-Speed Curing Ovens. In tances from one another. Those dis- particularly on conveyors with min- l -Inert gas blanketing may be re- some paint-baking .operations, ex- tances are multiples of twice the dis- imum tension in the chain and with tremely short baking times are re- quired with electron beam curing tances between the centers of the links and with some ultraviolet sources. turns less than 90 degrees outside the quired to cure the paint in the time al- in the chain. Sometimes several pul- oven. Where tensions in the chain are lotted. Conveyor travel may be fast or l Direct-gas-fired ovens have been the leys close together support a load bar most popular and universally ac- high and in baking ovens or other space in the oven may be limited. A which in turn supports the parts to be areas where it is difficult to lubricate coil coating oven is an example. With cepted for fabricated metal prod- finished. In this way the weight of the ucts finishing. One must, however, the individual rollers, sprockets or steel or aluminum coil, strap or tape part is distributed among four, six or smooth wheels are used to keep the travelling at 100 to perhaps 600 feet establish a new set of criteria if eight pulleys, rather than two. there simply is not enough gas avail- chain in its proper position under the (30.5183 m) per minute, a 20minute 4. Conveyor chain, which may be of I-beam and to minimize friction and bake would require a very long, unsup- able. Some shifting to other curing varying size, strength, weight, and methods is likely. wear of the conveyor system as the ported strip of metal in an oven. Thus, method of assembly. chain travels around a 90- or 180-de- it has become important to achieve 5. A drive mechanism, consisting of gree turn. rapid curing. There are several ways to electric motor, speed regulator, a pair Conveyors. 10. In conveyors moving small, accomplish this: The products to be of sprockets, and a special chain with painted must be moved through the light-weight parts, a steel cable is l Radiation curing, as described fingers to engage in the conveyor chain sometimes used in place of a chain. above. finishing steps in a convenient, re- to transmit the pulley force to a num- liable, predictable fashion, to min- 11. In another variation, pulleys are l Radiation from a high-temperature ber of links in the conveyor chain. imize film defects, and to allow max- mounted inside a hollow tube with a heat source close to the surface, as Sometimes there are several drive slot in the bottom of the tube. Good in infrared gas and electric heaters. imum quality and efficiency in the use mechanisms on a given conveyor, with of materials, labor, and energy. for moving light-weight parts. l Extremely hot air moving at normal their speeds synchronized. Drives also 12. Another variation involves trol- velocities. The most popular type of conveyor 1977 1977 PRODUCTS FINISHING DIRECTORY 39 38 PRODUCTS FINISHING DIRECTORY PAINT SUPPLY . . . lev-like devices or parts of trolleys lar in finishing rather large objects spray applicators are used, there will connected with a load bar. Four or that must be coated on all sides and be a paint filter, pressure regulator and more pulleys are on the I-beam and top, such as automobile bodies, truck pressure gauge. With some automatic there is no connecting chain from trol- or bus cabs or furniture. These sys- electrostatic application devices, it is ley to trolley or pairs of trolleys to tems involve a table, platform, or desirable to have even greater control pairs of trolleys. These trolley combi- dolly, usually with four wheels or cast- of the liquid paint flow to each appli- nations are moved from place to place ers. The object to be painted is posi- cator and sometimes variable-speed by one or more additional conveyors tioned on the platform. A pair of metering devices are used. that have a “dog” or “ear” or projec- tracks guide the wheels through the There are less elaborate systems for tion to engage on the load bar and various stages of the operation. A use where the volume of paint is move it at prescribed speed. This type chain or cable conveyor beneath the of conveyor, often called “power-and- platform moves the dolly. f?IRCULATING SYSTEM used in apply- free,” can be arranged to pick up work 14. Continous-metal-screen or belt- mg many different colors is made pos- from several conveyor-loading sta- type conveyors are also used in some sible by a sen’es ofpaintpumps in a cen- special situations. Usually large num- tral location. They feed paint from tions and move it onto a single main- supply tanks to spray stations. line conveyor; it can also change con- bers of small parts are being finished in veyor speed from place to place and these applications. Belt conveyors are PIPING brings the paint from the cen- switch trolleys to tracks directed to se- seldom used for the complete finishing tral supply in order to makepossible ap- lected operations. operation, from cleaning through plication of various colors. 13. Another type of conveyor, some- phosphatizing, drying, painting, and times called a floor conveyor, is popu- baking.

Liquid Paint Supply and Circulating Systems

In installations involving large vol- back to the mixing tank, with a pres- umes of paint, several colors, several sure gauge and pressure regulator to spray gun positions in a spray booth control return-line pressure. and/or several spray booth locations, 4. In some cases there is a strainer a central paint mixing and supply at the outlet of the return line to the room is often part of the finishing sys- mixing tank. An inlet for full-body tem. It provides paint that is uniform paint and another inlet for solvent in color and viscosity to all application reducer are also provided on some of stations. Such a system may include the systems. the following for each of one or more 5. The paint-mixing room and the colors or types of paint. storage room normally have fire wall, 1. Bulk storage tanks and/or drum fire doors, fire-extinguishing devices storage. and fire-signal devices as well as pro- 2. Pumps, filters and a pair of mix- tected floor drains. ing tanks with agitator and vent. 6. A variety of devices is installed at 3. Piping that travels from the the point in the circulating system pump to all application stations and where paint is used. If air-atomizing

1977 1977 40 PRODUCTS FINISHING DIRECTORY PRODUCTS FINISHING DIRECTORY 41 ULTRAFILTRATION, REVERSE OSMOSIS. . .

In a typical installation of ultrafil- smaller and where the distance from point of use. Air-operated piston This process permits the continuous or pumps are normal here, so compressed tration equipment in an electrocoat the mixing or supply area to the use periodic removal of oil as concentrated air supply is needed. system, the ultrafilter might be used to emulsion and the continuous return of area is relatively short. There are auxiliary control and sig- remove contaminants from the paint These systems may consist of a cleaner solution containing only very nalling devices which interlock electri- bath by discarding the ultrafiltrate. small amounts of oil to the washer. pump that covers the top of a drum. cally with such devices as ampere- If undesirable ingredients in the Sometimes the pump is mounted on a Disposal of the oil is simplified as it is platform with an elevator to raise and hour accumulators in the power sup- electrocoat bath are not the problem, concentrated and the life of the chem- ply of an electrocoat system. A specific then the ultrafiltrate can be used in lower the pump. The drum-mounted icals used in cleaning is increased. number of strokes of the pump can de- counter-current, post-electrocoating Reverse osmosis. In normal os- device may include an agitator to mix liver paint to the electrocoat system rinsing to recover the paint solids the paint in the drum. In more elabo- mosis water travels through a semi- when a specific number of ampere dragged out of the bath on the parts. permeable membrane to dilute a salt rate smaller systems, a pump may re- hours of current have passed. This is sometimes referred to as circulate paint between drum and solution on the other side. But the re- “closed-loop rinsing.” In most, if not verse can be made to occur: water can all cases, it is not truly closed-loop rin- leave a salt solution through a semi- sing, since some ultrafiltrate-to-drain permeable membrane, leaving a more Strainers, Filters, Ultrafilters, is required. concentrated salt solution behind. The most widely used ultrafiltration Pressure must be applied on the “salt” equipment involves several tubes in- side of the membrane to accomplish Reverse-Osmosis, Power Packs side a module, then a number of mod- this. ules in series and/or parallel. The Strainers and filters. Coatings, cron cartridge-type filter. Such a filter In practice this technique can be can allow particles up to about 3 mils electrocoat bath is pumped through used to concentrate water-soluble whether applied as liquid or powder, the insides of the tubes at a sufficient must be free of dirt, specks, lint, or for- (76.2 pm) to pass through. In other sys- chemicals while removing almost pure tems, filters as low as 10 to 25 microns flow rate to produce turbulent flow in- water. eign material. The thinner the film, side the tubes. Ultrafiltrate passes the higher the gloss and the longer the are used. Reverse osmosis systems generally through tiny pores in the very thin film is a liquid, the greater are the A wide variety of screen, cartridge, contain the following: and parallel-disc-type devices are membrane, is collected inside the shell l Tubular membranes mounted inside chances of seeing dirt in the film. Pamt of the module and released through a strainers and filters remove this dirt available for this purpose. multiple-tube modules, similar to Ultrafilters. Ultrafiltration utilizes valved opening in the shell near one the equipment for ultrafiltration from liquid coating materials before it end. The ultrafiltrate is then piped to a causes problems. membrane technology to separate par- but designed for higher pressure. ticles that would be too small to be re- rinse chamber or to drain, or to a re- l A closed loop, consisting of pump, When paint is received into a bulk verse osmosis unit. storage system, it is sometimes moved by conventional paint filters piping, and RO modules. from even smaller particles that are in, The other type of ultrafiltration l A high-pressure, low-volume pump strained before reaching the transfer unit involves a number of hollow, leaf- pump. A lo-mesh screen could be ade- or nearly in, solution in the paint. to push permeate into the closed- like units with porous membrane on quate. Before the paint enters the In electrocoating, ultrafiltration re- loop system, which mai be operated tains the pigment and resin particles the outside of the leaf. A number of the bulk-storage system it might be at 400-600 psi. of the paint bath and lets the dissolved leaves are mounted inside an enclo- pumped through a finer strainer or fil- l A system for bleeding off some of the salts and solids, solvent, resin frag- sure through which the electrocoat concentrated filtrate from time to ter-a loo-mesh screen or perhaps a bath is passed. Each of these enclo- 150-micron filter. ments, and some low-molecular- time. weight resin pass through the mem- sures is called a module. Modules are When paint is transferred from a l Appropriate gauges, controls, etc. brane. Two liquid streams result: a mounted in series and/or parallel. The In some electrocoat systems, some drum to a mixing tank in a circulating insides of the membrane leaves are system, some systems allow it to flow paint concentrate and an ultrafiltrate of the ultrafiltrate is subjected to re- or permeate; the latter contains the connected to tubes or pipes to bring verse osmosis so that the last water by gravity through a strainer or the permeate outside the module. screen, perhaps as fine as loo-mesh. water-soluble inorganic salts that may sprayed on the parts that have been After the paint is reduced, ready to have contaminated the bath, some Ultrafiltration may also be used to painted can be free from the chemicals spray and is being pumped from the solubilizing agent, some solvent, and separate or concentrate oil-in-water contained in the permeate. This re- mix tank to the spray guns, some sys- sometimes resin fragments or low-mo- emulsions from the first stage of power circulated last rinse can overflow into tems pass the paint through a 75mi- lecular-weight resins.52 washers or dip cleaning operations. the preceding rinses without adding 1977 1977 42 PRODUCTS FINISHING DIRECTORY PRODUCTS FINISHING DIRECTORY 43 PUMPS, RECTIFIERS . , . TOTAL FINISHING SYSTEMS. . . excessive water, as might be the case if plate-and-frame filters in effluent wa- terns may operate at 50 amperes. To illustrate the need for careful deionized water were used. ter treatment. Larger systems may require 200 to coordination of the design and capac- Pumps. A wide variety of pumps is 4. Gear pumps are used in some 3000 amperes. ity of the individual components, let’s used in painting systems. The princi- paint-circulating systems and in small Electrid interlocks. As one might look at a one-coat, enamel-on-steel pal types of pumps are as follows: sizes to meter paint to automatic guess, a wide variety of electrical inter- electrocoating system as an example. 1. Sump pumps are used in power spray guns. locks and options can be obtained with The physical dimensions of the washers to pump the solutions 5. Horizontal centrifugal pumps are electrocoat power packs, such as: electrocoating tank in a continuous through the pipes and nozzles. These used to recirculate water-ethylene gly- l Interlock with the conveyor to drop power-on entry system are controlled co1 mixtures through heat exchangers voltage to some preset level when centrifugal pumps can be mounted bv:-_I and chillers used to maintain tempera- the conveyor stops. with the suction opening deep within l The dimensions, weight and hanging the solution and with the impeller ture in electrocoating. They are also l Interlock with the conveyor moving pattern for the parts to be coated. used with pressure regulators in the through the tank to adjust voltage housing below the liquid level within l The conveyor speed. the covered tank. When this is done, tap water feed lines to deionize water by some set amount per unit of con- . The minimum coating time to water- and air-tight packing around systems to ensure uniform input water veyor speed change. achieve the required film thickness. pressure and consequently uniform l Current limit to reduce voltage to the shaft of the impeller housing is un- l The entrance and exit slope of the necessary. The entire pump assembly, flow rates. They are used to transfer prevent the current output from ex- convevor. with motor and bearings, can be re- paint or resin from tank trailers to ceeding some specific setting. l The distance needed between the moved from the system with a hoist, bulk storage tanks and from bulk stor- l A ramp to provide some time versus sides of the parts and the side of the without dumping the solution from age tanks to the point of use. voltage increase after receipt of a tank, to allow for cathodes, cathode the tank. Power Packs. In general, two start-up signal. guards, stand-off insulators and pip- Sump pumps are also used in the sources of direct current are used in l An ampere-hour accumulator and ing for circulation of bath. sump of electrocoat systems for the painting operations. The first supplies totalizer. l The amount of space under the above reasons and also to ensure that high voltage for electrostatic spraying l An ampere-hour accumulator to ac- parts when immersed, to accom- the pump does not pull in air and thus of liquid or powder coatings. It pro- tivate another circuit such as one modate parts that may fall off the cause foam. Some of these pumps have vides variable-voltage in the range of utilizing a paint feed pump after conveyor and make sure that they a short shaft from the bearing down to up to 100,000 volts, at very low cur- each predetermined number of am- do not contact parts hanging from the impeller. Others are quite long, rent. The amount of current varies pere hours. the conveyor. from unit to unit, but is measured in Finishing Systems. While finish- perhaps four to five feet. l The space under the longest part Trenches in the floor in the area of a milliamperes when used for electro- ing systems contain a number of com- needed for pipes, cathode or cathode power washer or the electrocoat tank static processes. ponents, each designed and selected guard mounting brackets and slope and rinse tanks often drain to sumps. The second type of electrical power for a specific function, the total system of the bottom of the tank. must be so designed and assembled as Sump pumps are used to move these pack (rectifier) is that used for electro- l The need for end, center-one-side, or waste waters to appropriate disposal coating-100-600 volts. In auto body to provide the desired quantity, qual- full-length one-side overflow weir outlets. Rinse tanks following electro- electrocoating or other applications of ity, cost, speed and reliability. And this and sump, and whether parts can be coating also use sump pumps. high-throwing-power electrocoat ma- must be done within the limitations of immersed close to this area without Care must be exercised in the oper- terials, output voltages of approxi- safety, air and water pollution require- moving into an undesirable position ation of these pumps to make sure mately 600 volts are common, as are ments, and with the available mate- in the tank. there is adequate head pressure so that current outputs of up to 1000 amperes. rials and people. l The quantity of paint to be con- they do not overload. In non-automotive and lower- The interrelationship of the various sumed relative to the quantity of 2. Air-actuated piston pumps are throwing-power systems, 300 volts will materials, process controls and capac- paint in the tank. used in supplying paint from drums to sufficeinmostcasesandsomesystems ities must be such as to provide a sys- l The relative importance of tank circulating systems or to electrocoat operate at about 100 volts. The tem that handles the total work loads, turn-over for the particular paint to tanks. amount of output current is a function including the unusual. It needs also to be used. 3. Piston pumps are used in some of the paint used, the film thickness, be designed and assembled to accom- l The maximum floor loading permis- paint-circulating systems to pump the maximum area to be coated in a modate anticipated variations of oper- sible in the manufacturing area paint from the mixing tank to the given time, and sometimes a function ating parameters and some degree of where the tank is located. spray guns. They are also used with of the design of the system. Small sys- human as well as machine failure. l Whether parts can enter the bath

1977 1977 44 PRODUCTS FINISHING DIRECTORY PRODUCTS FINISHING DIRECTORY 45 ELECTROCOAT SYSTEMS.. .

with cathodes located throwing-paints, when used in large to the cathode and the immersion phosphatizing to iron phosphatizing, power-on, time in the agitated bath after leav- near the entrance points, or tanks, require 600 volts. Some me- dry-off oven temperature might be re- dium-throwing-power materials re- ing the area between the cathodes. duced while still providing satisfactory whether cathodes need to be down- While not all of the above factors stream from the entrance point. quire only 100 to 300 volts. Others pretreatment. But it might be neces- will coat certain products at 50 to 75 are important considerations with all l The agitation system to be used, sary to change solvents or amounts of volts. electrocoating materials and systems, solvents used in reducing in order to such as side- or end-mounted draft- they have been in some systems. These tube agitators, side-mounted agita- l Short coating times and heavy film have the same “orange peel” and flow. build require higher voltages than factors can be isolated and evaluated One more example: a plant using tors only, or side- and bottom- in the laboratory much less expen- mounted pipes, with or without thin films with long coating times. heavily oiled steel for its fabricated sively than by rebuilding a production eductors. l Increasing the distance between the parts: Let us say it used a five- or six- cathode and the part to be coated system, stage hot-cleaning and phosphatizing l Quantity of recirculated bath to be Another interrelationship of mate- available. increases the required voltage in system and dry-off oven. The gas most systems. The author is famil- rials, operating parameters and equip- shortage requires reduction of tem- l Considerations involving future use ment design might be illustrated by and capacity of the tank or system. iar with a relatively high-speed, perature to almost “no heat” in clean- short-coating-time system in which considering a typical solvent-borne, ing and phosphatizing and in the dry- A sump is usually attached to the hand-spray, air-atomize painting op- coating tank. Paint flows into it over increasing the anode-to-cathode off oven. Result: oil runout at junc- spacing one inch (2.5 cm) increased eration for steel. tions of spot welded metal, and un- an overflow weir. It may be as small as The reducing solvent of the paint for 3-10 pet of the coating tank volume or the coating voltage 15 volts. In an- sightly paint. Several alternatives are other system involving longer coat- this type of system often must be ad- possible: as large as 3 or 4 times the size of the justed for variations in summer-win- coating tank. In systems involving a ing times, increasing the anode-to- l Preclean the steel before spot weld- cathode spacing by a foot (0.3 m) ter temperature in the spray booth; ing, perhaps by solvent vapor de- high rate of coating per unit volume of temperature of the metal being coating tank, such as one square foot only increased the coating voltage greasing method. requirement by 25 to 50 volts. painted; and temperature of the paint l Order steel with lower-viscosity oil. of surface to be coated per minute per being applied. l The substrate to be coated and its l Solvent wipe oil-run-out areas. gallon of tank capacity, it is desirable If one were to change from zinc to have a large sump to minimize pretreatment. l Reduce paint-baking temperature. changes in chemical composition of The current requirements for the the bath between additions of paint. power pack are a function of: l In systems involving small amounts of The square feet of surface to be Paint Materials coated per minute. area coated per minute per gallon of There are three commonly used l The film thickness required. ments about each type of material. tank capacity-perhaps one square methods for classifying industrially foot per minute per 140 gallons of tank l The minimum and- maximum im- Therefore, you need to have a broad mersion times of areas to be coated. applied paint: general knowledge of the materials capacity-it is important to minimize l By the nature of the resin used- sump size in order not to contribute to l The coulombic requirements to available to you and their attributes, yield the desired film thickness at acrylic, alkyd, epoxy, fluorocarbon, so that you can inquire about a given even greater tank-solids-turnover melamine, nitrocellulose, oleo- times. In the latter case, thirty-seven the minimum and maximum coat- type when a need arises. resinous, phenolic, polyester, sili- The principal types of resins used in working days per turnover might be ing times. cone, urea. reasonable. l The variations in coulombic re- chemical coatings include acrylic, al- l By its intended use-primer, top- Consider one more illustration from quirements of the paint with antici- kyd, cellulose acetate-butyrate, cellu- pated or allowable variations in coat, sealer, surfacer, touch up. lose nitrate, epoxy, ethyl cellulose, the electrocoat system: the direct cur- . According to the physical state of such factors as MEQ, specific resist- fluorocarbon, melamine (formal- rent source. Its cost is significant, and the material-solvent-borne, water- in the interest of energy conservation, ance, temperature and interfacial dehyde) nylon, polyamide, polyester, turbulence. borne, 100 pet solids liquid coating, polyethylene, polyurethane, Teflon, the selection and use of direct-current powder coatings, organosol, plasti- l The amount of rinse-off of paint in urea (formaldehyde), and vinyl (sev- sources need close attention. sol, lacquer. The voltage needed in a given elec- the drain and the rinsing of the eral types). products. Because of the immense variety of Perhaps the most widely used of trocoat system is a function of: coatings, there are major exceptions to l Time the parts are in the bath be- these in finishing fabricated steel prod- l The resistance or voltage character- almost all of the generalized state- istics of the paint. Some high- fore arriving at the closest position ucts are the acrylic, epoxy, polyester,

1977 1977 46 PRODUCTS FINISHING DIRECTORY PRODUCTS FINISHING DIRECTORY 47 RESIN SYSTEMS . . .

melamine and urea types. These resins certain special application techniques Coatings Evaluation: Quick and Simple are supplied in both solvent and wa- or for certain end products. Examples ter-borne forms with very nearly equal include powder coatings, often formu- Adapted for publication in the PRODUCTS FINISHING DIRECTORY properties in either form. They can be lated from vinyl, Teflon, polypropy- from ‘A Few Shortcuts to Coatings Comparison,” PRODUCTS FIN- tailored for a wide variety of applica- lene, nylon and epoxy resins; coatings ISHING, March 1976. The original source of the information is a liter- tion methods, including dip, flow coat, to cure without baking, such as polya- ature sheet from Conforming Matrix Corp., Toledo, Ohio. manual, electrostatic and airless mide, polyurethane, alkyd and some spray, roller coat and electrocoat. polyesters; and coatings that dry (not Suppose you have two organic coat- one-quarter inch mandrel bend test. They are the work horses. Adhesion cure) without baking, such as nitro- ings to evaluate. Here are a few tests Other resins have properties that Use a letter opener or razor blade to cellulose, vinyl, ethyl cellulose and you can perform right at your desk, make them particularly adaptable for certain alkyds. without going through detailed and scribe a tic-tat-toe pattern (cross time consuming laboratory analyses. hatch with about one half inch Hardness squares) on the paint surface. Now Take a set of lead pencils with a press a transparent adhesive tape Properties of Principal l&sins over the cross hatch area. Snap it off. hardness range of H to 4H. Sharpen Acrylic. Pale color; tolerance for the pencils; now flatten the points so If the paint came off it had poor adhe- and low-temperature force-dry alkyds sion. Be sure to SNAP off the tape. A heat during baking and thus color uni- also have a place in finishes calling for they have a chisel face. Hold at a 45 formity in production; color retention deg angle, push forward and press. gentle pull off is not too good a test. modest exterior durability. - Color on exposure to heat, sunlight or dark- A wide variety of properties are at- The soft pencil should break. (The ness after baking and thus color stabil- lead that is, not the pencil.) The paint Sometimes, if you rock the test tainable, but each outstanding char- panel in your hand the color seems to ity in exterior exposure; minimum acteristic of a particular alkyd resin is should not rupture. Now repeat with chalking under ultraviolet light expo- the next harder pencil. Continue up change. Go to a window that has usually accompanied by a disadvan- north light and now check the panel. sure; when properly modified with tage that limits its use or requires until the paint ruptures instead of the other resins and chemicals, an excel- lead breaking. The coating resisting You will usually see a difference. The blending with other alkyd resins or reason is some colors change under lent combination of hardness, adhe- other modifying resins. For example, the highest pencil number is the sion, and resistance to abrasion, chem- harder. 4H is pretty good. Never test a fluorescent light or white light. In the very good heat resistance and color re- lab they have special lights that com- icals, corrosion and impact; somewhat tention can be obtained with one type lacquer when it has just dried. Usually higher cost than alkyds. they require 24 hours before they are pensate for these variations. of alkyd, but it has poor adhesion to If you want to check for color stabil- Acrylic powder coating resins are steel and poor stain resistance. An- ready to be tested. A baking enamel used where thin films without primer can be tested after cooling. ity-especially red and gold pig- other alkyd resin offers good adhesion ments-place the panels in a south are required and where good gloss and on steel and good stain resistance but Abrasion weathering are needed.3d,50 Now use the eraser. Using the same window. But first put a square of poor heat resistance and poor color re- Oleoresinous. Oleoresinous coat- pressure and a new eraser on each masking tape over a large area. At a tention in dark, humid conditions. later date (determined by results) take ings are those made using ingredients Cellulose Acetate Butyrate or coating, make a series of short coming primarily from natural sources strokes and count. One coating the panels and compare masked and Propionate. These resins are avail- unmasked surface of each color for such as rosin and vegetable oils. They able as powder coatings. Extremely should outlast the other. Thirty were the predecessors of the alkyds strokes is pretty good. fade. With different coatings one will tough coatings in a range of colors, usually be better than the other. and the followers of oil paints, being with good resistance to outdoor Flexibility somewhat faster drying and producing If the coating is on a thin metal test Gloss weathering. Coatings reputed to meet harder coatings than the oil paints. panel, use your pencil as a mandrel. Some coatings require a reflective FDA specifications for use in contact brilliance. If you are comparing parts, They are still used in air-dry and low- with food are available. X3 With the painted surface on the out- temperature drying product finishes side, bend the sheet over the pencil look into the part and find a reflection High fusion temperatures are re- of an overhead light fixture. One coat- and as the primers in certain cases. quired, but relatively low costs per very slowly and watch for a paint rup- Alkyd. The alkyd resins were ex- ture. (360-deg around a pencil is ing should show more detail than the square foot per mil are reported. tremely popular a quarter of a century rare.) One coating should rupture other. That will be the more glossy of Primer required for best adhesion. the two (assuming substrates are the ago and still have important places in Cellulose Nitrate or Nitrocellu- (crack) at a lesser angle than the the industry. Cost is moderate. Air-dry other. This is a rough equivalent to a same). lose. Nitrocellulose resin is used in

1977 1977 PRODUCTS FINISHING DIRECTORY 48 PRODUCTS FINISHING DIRECTORY 49 $7 RESIN PROPERTIES . . .

Table R air-dry, lacquers for a variety of pur- the form of a liquid coating-either sol- vent or water-borne-but is used as a poses, such as those for toys and novel- General Properties of Resin Systems ties, color cards, wood furniture, powder coating where extreme resist- quick-dry adhesives, “airplane ce- ance to a wide variety of environments ment” and paper coatings. Quick dry- other than strong acids is required. ‘* ing. High-cost organic solvents must High fusion temperature and rela- be used to make suitable coatings. tively high cost per square foot per mil Epoxy. A wide variety of modi- are reported. Good sliding contact fications is marketed. There are solu- properties. tion epoxies, modified epoxies and Phenolic. They’re used in applica- epoxy esters. Epoxy resins are also tions requiring hardness, excellent ad- used to modify other resins. Epoxy fin- hesion, and resistance to corrosion and Treated Metal IG IF-G 1 P-F IVG IF-G (VG IVG G P.G G E ishes usually have good adhesion to chemicals. But the application must AlkaliResistance 1 G-E IF IP-F IE IF. IE IG c r, I: c metal, good to excellent corrosion re- tolerate high-bake, dark-color coat- Exterior Durability E G F F P-F F P i cc i ; sistance, alkali and detergent resist- ings which may discolor light-colored CorrtionResistance G G P-F E FE G flexibility FG G E- G G F I: F F ance. Their resistance to ultraviolet enamels applied as topcoats. I I , I I II2 I I: Ir I c I c light and heat is poor. May require rel- Polyester. There is a wide variety Heat Resistance 1 iG Ii-F 11 1; 1; 1; 1; 1; I; 1; 1; atively high baking temperatures and of polyesters. Perhaps the best known cosl 1 High IMed. I High IMed. 1 Med.lHlgh IHigh 1 HighlHlgh IVery IVery high-cost solvents. Epoxies have been is the type used in “fiberglass” boats, to High High Hiah the most popular powder coatings and shower stalls, bathtubs and fishing - “Availability” abbreviations: W = Water-borne Other abbreviations: E = Excellent VG = Very Go several different modifications are rods. There is more polyester resin od S = Solvent-borne E = Electrocoatinn 1 G = Good F = Fair P = Pm available.‘i.‘d.‘Y than glass fiber in these coatings. The Ethyl Cellulose. These resins are color coatings on the surface of these little known to most product finishers. products often contain acrylic-resin They are used for specialty coatings modifications to improve color stabil- Polyester powder coatings are used that needed for curing a solvent-borne such as strippable coatings, hot-melt ity and resistance to chalking when ex- where toughness, dielectric properties acrylic; 45 pet of that for a typical coatings for long term or severe expo- posed to sunlight. and adhesion without a primer are re- powder coating; 40 pet of that for a quired. Outdoor durability and rea- sure and coatings for short-term pro- Polyester resins are also used in high-solids polyester; and 45 pet of tection of parts in storage. clear coatings for wood products and sonable cost are also attributes. Typi- that required for curing a typical wa- Fluorocarbon. These resins were may be formulated to cure very rap- cal applications: pipe, transformers, ter-borne coating (Table II).3L introduced a number of years ago as idly when exposed to electron beam or guard rails, wire goods and hardware.“’ Urethanes can be cured in 20 min at “super’‘-weather-resistant coatings. ultraviolet light sources. Some poly- Silicone. Used in specialty applica- 180F (82C). Pot life is sometimes a lim- Reported to have two to five times the ester resin coatings are “air inhibited” tions requiring resistance to heat and iting factor. exterior durability of other resins during cure. They will leave a tacky discoloration. Some of these products Vinyl Resins. Supplied for a wide mentioned here. They are supplied as surface after the balance of the resin is cost two to five times as much as the range of applications. Good abrasion resin or pigmented-resin dispersions in cured if cured in contact with air. more conventional coatings but they resistance and general durability. non-solvent organic liquids. Polyester resins combined with do provide major improvements in Some solvent-borne vinyls are used in Melamine. Melamine finishes are other resins are used in coil coating properties. thin films on beverage containers, usually modifications of some other and electrocoating. Coatings for wa- Urethane. Has become more popu- where minimum taste contribution resin such as an alkyd or acrylic. They ter-borne, solvent-borne, and so-called lar as a result of the energy crisis. from the coating is required. Some are impart hardness, stain, chemical, heat, 100 per cent solids coatings also utilize When energy for operation of a power used in wood-coating lacquers to im- and weather resistance. But they also polyesters. They are used in patching washer and dry-off oven is excluded, part toughness, flexibility and water increase cost and they may contribute compounds for repair of auto bodies, then the energy required for a 20-min- resistance while still allowing fast air to fouling or flatting in gas-fired ovens for repairing cement floors and for re- ute bake on 24-gauge steel products at dry. containing acid fumes or fumes from a pair of chemical storage tanks. Also the rate of 12,000 sq ft (1115 sq m) per Some vinyl-resin coatings. require vapor degreaser. are there applications in encapsula- hour in a conventional direct-gas-fired special primers to provide adhesion on Nylon. It has not been applied in tion of electrical components. oven is reported to be only 27 pet of metal. A variety of additives is re- 1977 1977 50 PRODUCTS FINISHING DIRECTORY PRODUCTS FINISHING DIRECTORY 51

._- P quired to maintain color stability and heat resistance. Pollution, Energy, OSHA Vinyl resins have been popular as powder-coating resins, too:‘“-.” They Air-pollution problems. The pas- contaminants in a finishing plant are are used on appliances, electrical prod- sage of Rule 66 in Los Angeles County, as follows: ucts, shelving, hardware, furniture, Regulation 3 in the San Francisco area Pretreatment chemicals. Oils, sporting equipment and coil-coated and similar regulations in other areas suspended matter, heavy metals, al- steel. of the country, as well as federal clean kalis, acids, phosphates, hexavalent orfi Vinyls are the basis for organosol air and clean water acts is encouraging trivalent chromium, biodegradeable and plastisol coatings for heavy-film paint users to discontinue using mate- materials. Some plants have had to applications. Most if not all of these rials and methods which require va- change their processes or treat the wa- needs can be met with powder coating porization of organic solvents. ter before discharging into surface techniques and materials, too. Many choices are available to re- streams. There has been higher toler- Polypropylene. As a powder coat- duce these emissions. Each has its own ance for these materials in large mu- ing, polypropylene provides good flex- attributes for finishing certain prod- nicipal sewer systems, but this, too, ibility as well as resistance to impact, ucts in certain locations. Here are the may become history. abrasion, solvents, detergents, alkalis, most popular choices: Spray-booth curtains. Chemicals acids, humidity and salt spray. Good Electrocoating. The solvent con- and suspended paint particles from a dielectric strength and use in contact tent of the paint as used is often below water-wash spray booth require treat- TWO-COMPONENT urethane coating is 0.5 pet and almost always below 2 pet. ment before discharge. premixed, then sprayed on bus body. with food is also reported. For best re- sults, water quenching after fusion of In certain electrocoating materials the Post-electrocoat rinsing and per- the powder coating is required; a solvent content is higher but certainly meate-to-drain purging of electrocoat primer is usually needed, too.39,4” below 20 pet by volume of the volatile systems cause high BOD (Biological portion of the paint as applied. Oxygen Demand) in the effluent, and Water-borne coatings for other consequent additional treatment. methods of application. The volatile Regeneration of deionizers or portion contains 20 pet or less organic other ion-exchange processes can re- solvent. sult in heavy metal or BOD contami- Powder coatings. The decrease in nation of effluent. weight on baking is 10 pet or less of the Stripping of work hangers or re- weight of the cured coating. jected parts in water solutions also at High-solids coatings. The paint as times produces undesirable effluent. applied is expected to be 80 pet solids. Safety regulations. The Occupa- Exempt solvents. Conventional tional Safety and Health Act of 1970 solids content. It appears that envi- and the establishment of the National ronmental regulations will require Institute for Occupational Safety and that exempt solvents also be elimi- Health within the department of nated as air-pollution laws tighten. Health, Education and Welfare have Pre-coated metal. Have someone created a major impact on manufac- . ENAMELS . PRIMERS . THINNERS else do the painting, in other words. turing management. Catalyzed, air-dry coatings . R.M. GOLDS . HAMMERS l CORIHYDE or One example is the restraints placed other 100 pet solids materials. l WATER-SOLUBLE ENAMELS upon use of certain volatile solvents Water-pollution problems. The and chemicals such as chlorinated sol- l AIR-DRY, LOW BAKE FINISHES Environmental Protection Agency vents, ketones and vinyl compounds. DURALAC CHEMICAL CORP. 84 LISTER AVE. NEWARK, N. I. 07105 and local authorities require that liq- OSHA restricts the exposure per- TeleDhone: (2011 589-2946 uid effluent be free of certain contami- mitted for persons working with these nants. Some of the sources of these solvents.

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