United States Patent (19) 11, 3,969,195 Dötzer et al. (45) July 13, 1976

(54) METHODS OF COATING AND SURFACE 3,448, 127 6/1969 Dotzer...... 204f14 R 3,672,965 6/1972 Harwood...... 204/14 N FINISHING ARTICLES MADE OF METALS 3,691,030 9/1972 Stroszynski...... 204/33 AND THEIR ALLOYS 3,699,013 10/1972 Miyata...... 204/32 R 75 Inventors: Richard Dötzer; Klaus Stöger, both of Nurnberg, Germany FOREIGN PATENTS OR APPLICATIONS (73) Assignee: Siemens Aktiengesellschaft, Munich, 1,047,450 12/1958 Germany...... 204/14 Germany Primary Examiner-T. M. Tufariello (22 Filed: Oct. 26, 1972 Attorney, Agent, or Firm-Kenyon & Kenyon Reilly (21) Appl. No.: 300,906 Carr & Chapin Related U.S. Application Data 57 ABSTRACT 63 Continuation-in-part of Ser. No. 249,279, May 1, Articles made of ferrous, non-ferrous and light metals 1972. and alloys thereof, e.g., aluminum, beryllium, magne sium, molybdenum, steel, tantalum, titanium, tung 30 Foreign Application Priority Data sten, vanadium and zinc and their alloys, are pre May 7, 1971 Germany...... 2122610 treated before coating and surface finishing in an an Oct. 28, 1971 Germany...... 2153831 hydrous, inert, aprotic liquid, and subsequently elec troplated with aluminum, cadmium, indium or zinc in 52) U.S. Cl...... 204/14 N; 204/32 R; an aprotic organo-metal electrolyte essentially free of 204/33 molecular oxygen and water and, optionally, addition 51) Int. Cl...... C25D 1700; C25D 5/34; ally finished by anodizing, chemical oxidation or diffu C25D 5/44 sion. The pretreatment may be by erosion with finely 58 Field of Search...... 204/39, 145 F, 33, 14 N, divided abrasive particles suspended in such liquid and 204/32 R; 134/2, 3, 6, 7, 9 impinged upon the surface of the article by hydraulic jetting, or with an aprotic liquid by the liquid-drop 56) References Cited erosion method. Alternatively, the pretreatment may UNITED STATES PATENTS be by electrolytic action in a circuit where the article 2,873,233 2/1959 Schnable...... 'ss ss ss. 204/32 serves as the anode and is immersed in an anhydrous, 2,893,931 7/1959 Boyett...... 204/33 aprotic electrolyte. Articles so pretreated and electro 2,899,367 8/1959 Veeder...... 204/32 R plated are thereafter more readily surface-finished or 2,901,383 8/1959 Lebsanft...... 134/7 mechanically shaped. 3,214,867 1 1/1965 Henning...... 134/7 3,268,421 8/1966 McGraw ...... 204/39 11 Claims, No Drawings 3,969,195 1. 2 developing, thin oxide coating (rutile) provides excel METHODS OF COATENG AND SURFACE lent corrosion protection in oxidizing media. Although FINISHING ARTICLES MADE OF METALS AND this oxide coating can be increased in thickness THER ALLOYS . . . . through anodic oxidation, it has in contrast to the elox This application is a continuation-in-part of our co ation coating of aluminum (created by anodizing), a pending application Ser. No. 249,279, filed May 1, deeply violet to bluish-red color and does not possess 1972. the honeycomb structure which is inherent in the color This invention is directed to the art of electroplating less eloxation layer of aluminum and which provides and surface finishing articles of metals and their alloys, the superior penetration (advantageous for dyeing or and more specifically is directed to pretreating the O staining) and solidification (sealing) properties of the surface of such an article before electroplating it with eloxation coating. Also, articles of titanium do not aluminum, cadmium, indium or zinc, after which it may attain the bright color hue and the good electrical con be further surface-finished, such as by anodizing, or ductivity of aluminum. mechanically shaped, as by drawing or stamping. Zinc and zinc alloys also develop oxidic protective The coating and surface finishing of articles made of 15 layers on the surface, under the effect of atmospheric light metals, particularly beryllium, magnesium, alumi influences, which protect the underlying metal from num, titanium and zinc and their alloys, is often neces further corrosion. In contrast to aluminum, no methods sary, because they are relatively base metals whose are now known for treating zinc. that would permit surfaces rapidly develop a fundamentally oxidic coat reinforcing (thickening) the protective layer by anodic ing when exposed to the atmosphere. Such an oxidic 20 oxidation or make it possible to build-up oxide layers coating usually protects the underlying metal against whose structure permits dyeing or staining. further corrosive attacks. However, the surfaces of Coating by electroplating and surface finishing of the articles made of such metals properly cannot be fin aforementioned light metals in aqueous or protic elec ished or coated in aqueous or protic media, due to the trolyte baths is greatly impeded by the very rapid devel characteristics of the metals and oxide coatings. 25 opment of oxide or hydroxide surface coating in air or Attempting to remove the oxidic coating by means of in aqueous hydrous pretreatment and electrolyte me sand blasting causes the immediate formation of a new dia. The surface coatings which are always present in oxide coating in relatively base, oxygen-affinitive met aqueous media prevent or at least greatly complicate als, due to the ambient air, and this oxide coating the direct electroplating of the basic metal without makes difficult or even prevents subsequent electro 30 proper pretreatment and impair, the electro-crystalliza plating. This is a major disadvantage, since the excel tion, the adherence, and the homogeneity of the addi lent mechanical properties and the low specific weight tional metal added by electroplating. As a result, elec of these metals make their utilization increasingly im troplating articles made of light metals, especially of portant in the construction of air-and space vehicles beryllium and magnesium, from aqueous electrolyte and automobiles. 35 media remains an unsolved problem. Most of all, the The effect of corrosion protection depends very electroplating of aluminum and its alloys with other largely on the degree of purity of the metal, and, in metals still causes considerable difficulties. alloys, on the type of alloying constituents. Generally, : It also is known that the mechanical forming of mate the rate of corrosion will decrease as the degree of rials by drawing, deep-drawing, extruding, pressing, purity of the metal increases. Alloying constituents 40 embossing, stamping, squeezing, rolling, etc., can be should not be selected only with respect to their favor facilitated and improved through the use of auxiliary able influence upon the corrosion behavior of the base substances such as drawing soaps, pastes, fats, oils, metal but, most of all, with respect to the improvement lubricants and the like, and that considerable advan they impart to the mechanical, processing and casting tages as to production and economy can be obtained characteristics of the base metal. Iron that is kept ex 45 through the choice of suitable auxiliary agents for the tremely pure through zone pulling and suspension melt material and the tools. ing will virtually not corrode in moist air. Coating of the material to be formed with metal can “Electron metal', which is an alloy with 90% and be of advantage in the forming process. According to more of magnesium and, depending on usage, including the discussion in the paper “Technology of the Hard varying amounts of aluminum, zinc, manganese, cop 50 Superconductors' by H. Hillmann in Zeitschrift fuer per and silicon, can be processed very easily by ma Metallkunde, Vol. 60, No. 3, particularly at pp. 162 chining, but quickly becomes subject to atmospheric and 164 (1969), for instance, wire material coated with corrosion. The die-casting aluminum alloys which are copper shows better than 99% cold forming of a niobi particularly desirable for manufacturing, such as the um-titanium alloy, which in itself is very hard and al alloys conventionally denominated DG AlSil0(Cu), 55 most brittle. DG AlSil2 and DG AlSi6Cu3, cannot be finished by It has now been found that the shaping of articles anodizing or, if anodized, will result in an unsatisfac made of ferrous, non-ferrous heavy- or light-metals can tory quality and have an unsightly gray color. be facilitated considerably if the substrate metal has Beryllium and beryllium alloys which are preferred been electroplated with high-purity aluminum, zinc, modern construction materials due to their excellent 60 cadmium or indium. The formability of the metal is strength at a very low (1.86) specific weight lack a considerably improved, and at the same time its surface dense, adhering and non-toxic surface-protection film is protected and upgraded with respect to the proper to protect them against severe corrosive attack. ties which are of technical interest. Shaped articles Titanium and titanium alloys find increasingly which have been electroplated according to the inven greater use in air-and space vehicles, as well as in ma 65 tion and which have been formed by drawing, emboss chinery construction and in the chemical industry, ing, pressing and stamping, as well as by squeezing, because of their excellent mechanical properties at a rolling and by explosion methods, possess the mechani relatively low (4.51) specific gravity. Their quickly cally and technologically advantageous properties of 3,969,195 3 4 the substrate metal, such as high strength, magnetism polarity reversal. The article is protected from expo and high electric conductivity, together with the partic sure to moisture and oxidizing conditions after being ularly useful surface properties of the named electro pretreated and until it has been electroplated. After plating metals, such as for instance, corrosion protec electroplating, the article may be provided with an tion, ultrasonic weldability and solderability, anodic eloxal coating, optionally later stained with dye, by and chemical oxidation, which can be combined with anodizing. Also, it may be surface-finished by chemical further possibilities for surface finishing. In the case of oxidation or metal diffusion techniques. rolling, squeezing and explosion forming processes, the (As used herein to refer to the pieces of metal being electroplated coatings fulfill a function which saves and treated in accordance with this invention, "article' protects the substrate metal and ideally transmits O refers broadly to metal (including alloys) in various forces due to work hardening. stages of fabrication into an article of manufacture, and Metals, particularly ferrous and heavy metals, pro may be in the form of sheets, bars, slabs, strips, mold vided with an electroplated coating in accordance with ings, die castings, stampings, extrusions, and the like, the invention as an auxiliary forming agent can be de and assemblages of two or more pieces joined to formed to a greater extent than heretofore. The draw 15 gether). ing properties, for instance, can be improved. Articles It has been discovered that the surface of articles of with thinner walls can be produced, and it becomes metals and their alloys can be electroplated with an possible to work metals which heretofore could be adhesive, homogeneous and dense coating, if the sur shaped only with difficulty or not at all. Because of the face of the article is first pretreated in an anhydrous, unusually high ductility of the above-mentioned elec 20 inert aprotic liquid and subsequently electroplated in troplated metals, the problem of cutting and stamping an aprotic, organo-metal electrolyte which is substan edges becomes manageable, with proper design of the tially devoid of water and molecular oxygen, and, op tools, through coating and compression welding. tionally, further surface-finished. Accordingly, it is an object of this invention to fur The pretreatment according to the present invention nish a process by which light metals and alloys of them 25 in aprotic organo-metal electrolyte media, free of oxy may be first pretreated to remove surface layers of gen and water, produces bright light-metal surfaces, oxides and/or scale and thereafter electroplated with a free of surface films, which do not corrode, thereby thin coating of aluminum, by which process the light allowing an ideal, immediate deposition of the protec metal article is provided with a tightly adherent, uni tive metal upon the surface of the light metal. form layer of highly pure aluminum. 30 When necessary, the surface treatment of the articles Another object is to furnish a process by which light may be effected under the exclusion of air in an atmo metals, especially beryllium, magnesium, titanium and sphere of inert gas. This provides a bright surface with zinc, may be coated with a thin coating of aluminum out surface film for these metals which would otherwise and thereafter anodized to furnish an eloxal coating on react in aqueous or protic media or when exposed to the surface thereof. 35 air, and develop oxide-hydroxide or salt-like surface A further object is to furnish a process by which films which would prevent further electroplating, or at metals, particularly ferrous and non-ferrous heavy met least interfere therewith, and reduce or impair the ad als, may be coated with a thin coating of aluminum, hesiveness of the protective metal being plated onto the cadmium, indium or zinc which facilitates the subse surface. quent mechanical shaping of the coated metal. 40 The above-mentioned electrolytic metals, which are Broadly stated, in a process of electroplating with relatively soft by nature, when electroplated on the aluminum, cadmium, indium or zinc, an article made of surface-treated substrate metals under oxygen- and a ferrous or a non-ferrous heavy- or light-metal or an water-free conditions are strongly adherent, with a alloy thereof, the invention is the improvement of pre purity of better than 99.99%. The strong bonding to the treating the surface of such an article with an anhy 45 base material, which is necessary if the electroplated drous, aprotic liquid for the purpose of removing scale metal is to serve as an auxiliary forming agent, is and exposing bright metal, and subsequently electro thereby assured. Functional coatings such as, for in plating the article with aluminum, cadmium, indium or stance, copper or nickel, may already have been ap zinc in an aprotic electroplating electrolyte. The pre plied to the substrate metal to facilitate solderability. treatment is advantageously done by eroding the sur 50 The auxiliary-layer or electrodeposited-metal layer, face of said article with finely-divided abrasive particles respectively, can also be joined to the substrate even suspended in such anhydrous aprotic liquid, which may more intimately prior to forming by a heat treatment, be, for example, a normally-liquid hydrocarbon, a halo by virtue of diffusion processes. Because of the consid genated hydrocarbon, a perhalogenated hydrocarbon erably higher purity of the metals electroplated on the or a silicone oil, or an appropriate mixture of them. The 55 surface of the substrate from the aprotic, oxygen- and liquid may be impinged against the surface of the metal water-free, organometallic electrolytic media, particu by hydraulic jetting under high pressure, or by the larly advantageous surface properties are obtained, and liquid drop impact erosion technique. Alternatively, at the same time a coating is created which is valuable the surface pretreating may be done by passing an from the viewpoint of possible uses of the coated arti electrical current through the article electrically con 60 cle. nected to operate as the anode of the circuit, while it is The process may be applied to light metals, such as immersed in an aprotic electrolyte essentially devoid of aluminum, beryllium, magnesium and titanium, and to water and molecular oxygen. Thereafter, the article is ferrotis and non-ferrous heavy metals such as, for in electroplated in an aprotic electroplating electrolyte. stance, titanium, zirconium, hafnium, vanadium, nio The electroplating electrolyte optionally may be one 65 bium, tantalum, molybdenum, tungsten, rhenium, or in having the general formula MXAlR'R''R + (m) sol general, materials which exhibit sufficient plasticity to vent, as described hereinafter. The electroplating may be worked by one of the mechanical forming processes be conducted employing a pulsed current and cyclical mentioned above and which have sufficient electrical 3,969,195 5 6 conductivity or can react at their surface so that they It is noteworthy that this embodiment of pretreating can be cathodically coated in aprotic, oxygen- and surfaces requires few process steps and works without hydrogen-free electrolytic media. Even though the the need of aqueous etching and rinsing baths and advantage of the method according to the invention is therefore also eliminates waste water disposal prob particularly great in connection with aluminum-plated lems. ferrous materials, the advantages of better formability The surface pretreatment according to the invention and surface finish also exist with a coating of electro may also be effected through liquid-drop impact ero plated cadmium, zinc and indium. sion, with inert, anhydrous, aprotic liquids. Such a In the following text, electroplating of aluminum method is described, for example, in German Pat. No. onto light metals will be described illustratively. O 1,614,690. This embodiment of surface treatment is In a preferred embodiment of the present invention, particularly suitable for strip and sheet material for the pretreatment is effected by hydraulic jets having continuous operation and represents the method that is abrasive particles suspended in oil or other inert liq most suitable (“best matched') to the material being uids, such as, e.g., paraffin oils, high-boiling hydrocar treated. It is characterized by the following process bons, chlorinated hydrocarbons, silicone oils, and the 15 steps: : like. A specific system employs a light oil and corun 1. manufacturing sheets or strips of the metal to be dum powder having particle sizes between about 50 treated, optionally wound on a reel or drum for and 200 microns, with jet pressures between about 1 feeding into the process; and 10 atmospheres gauge, preferably 3 to 7 atm. As a 2. pretreating the metal by liquid-drop impact ero 20 sion (in which the drops of liquid fall under the propulsion means, the oil itself can be circulated or influence of gravity) with benzene or toluene, op accelerated with compressed air or an inert gas, such as tionally after preheating the metal; and nitrogen. The abrasive particles may be corundum, 3. immersing the metal into the electrolyte bath em silicon carbide, glass beads, and the like. : ployed for electroplating. The hydrophobic liquid film which surrounds the 25 For safety reasons, the liquid-drop impact erosion is abrasive particles displaces air and moisture during its conducted in an atmosphere of gaseous nitrogen or impingement upon the metal surface to be cleaned, so perhalogenated hydrocarbons. that the abrasive particles break through the oxide The aforementioned advantages also apply to this surface layer within the liquid film and expose the bare procedure. metal surface, which is being protected by the liquid 30 A third suitable surface pretreating method is the film against the access of air and moisture. anodic removal of a thin surface layer of the light-metal The pretreatment according to the method of the article in an aprotic organo-aluminum electrolyte me present invention is a relatively gentle mechanical dium, more particularly, in electrolytes containing alu treatment of the surface of the article. The surface minum ethyl and/or aluminum methyl. The ethyl or removal takes place within a range of only a few tenths, 35 methyl radicals which are generated at the anode dur to a few microns of layer thickness. Thicker oxide and ing the passage of current, dissolve the light metals into scale layers can be removed beforehand by sand blast liquid metal alkyls (MR): ing or by chemical pretreatment. This is not required, Be+ 2 R.-P. BeR however, for newly processed greased or oiled articles. Mg+2. R. - MgR, The oxide layers which also develop at room tempera 40 Zn + 2 R.- ZnR ture on dry surfaces of light metals can also be directly Al + 3 R. - AlR removed by hydraulic jets with abrasive particles sus Ti -- 4 R. --> TiR pended in oil. It is a particular technical advantage, of While articles made of beryllium or aluminum may also this invention that greased articles can be immediately be anodically dissolved in aluminizing electrolyte subjected to the surface pretreatment described herein. 45 media containing halides, particularly hydro-fluorides, The surface-finishing method or our invention, which this cannot be done with articles made of magnesium or is suitable for all materials, has the following processing zinc, because of the formation of insulating surface steps, when conducted by means of hydraulic jets: layers of a metal halide, especially MgF2 or ZnF. Elec 1. mechanical fabrication of the article; trolytes suitable for effecting anodic pretreatment of 2. pretreating the surface of the article with a hydrau 50 any of the light metals referred to herein are the tetra lic jet of an abrasive suspended in an aprotic liquid, alkyl alanate-complexes which are free of halide ions, preferably oil; e.g. . 3. removing an oily or greasy film, if any be present, NaAl(CH)), NaAl(CH3)), RNAl(CHs)). from the article by immersion into a suitable sol The mixed sodium-potassium salts of the tetraethylala vent, such as perchloro-ethylene (sometimes de 55 nate, which melts at 70°C, is particularly advantageous. nominated PER); - The sodium salt first melts at 128°C. Light metal arti 4. thereafter completing the de-greasing by PER cles which are anodically treated in these molten elec vapor de-greasing; trolytes and thereby pretreated with respect to their 5. promptly immersing or rinsing the article in tolu surface, may be immersed under inert gas into the ene, optionally, with ultra-sonic vibration; and, 60 electroplating cell, still wet with the pretreating elec 6. promptly immersing the article into the electrolyte trolyte, and electroplated with aluminum by means of bath employed for electroplating. cathodic action. By routine experimentation varying the type and size With articles made of beryllium and aluminum, the of the abrasive particles, the viscosity of the aprotic anodic surface pretreatment can be carried out directly liquid, and the jet pressure, suitable operating condi 65 in the electroplating cell and the bare metal surface can tions can be obtained for each metal and each surface be electroplated with aluminum by means of polarity characteristic, and bare metal surfaces, free of surface reversal. This particularly favorable embodiment of the filing, can be obtained. , ; surface pretreatment method in an aprotic electrolyte 3,969,195 7 8 medium, free of water and oxygen, comprises the fol negative ion (e.g., CN, Nar); R" is selected from the lowing steps: . '. same class of radicals as is R' and on any specific i. Vapor-degreasing with PER the article to be molecule of the complex, may be the same as or dif treated and draining excess liquid from its surface; ferent from R'; and m (mols) may be in the range of 2. Washing, or rinsing, the article with toluene, op 5 0-5. Suitable solvents are, e.g., aromatic hydro tionally with ultra-sonic vibration; carbons, particularly toluene and xylene, and ethers, 3. immersing the article, wet with toluene, into the electroplating bath, electrically connecting the preferably higher-boiling ethers, such as tetrahydro article as the anode of the circuit, and anodically furan, dipropyl-dibutyl ether, dioxane, etc. Electrolytes charging it for a time, about 15 min., sufficient to O of this type are disclosed, for instance, in German Pat. remove the surface film or scale, optionally with Nos. 1,200,817 and 1,236,208. The organo-aluminum concurrent movement (sometimes referred to in electrolytes may be used alone, or in a mixture. In : . . the electroplating art as agitation) of the article; order to increase their conductivity, they may be and, . diluted with aromatic hydrocarbons, e.g., toluene. 4. reversing polarity and electroplating aluminum 5 The upper limit of the bath temperature during elec onto the surface of the article... troplating is determined by the thermal stability of the When articles comprising magnesium, zinc or tita electrolyte and the boiling point of the solvent if any is nium are treated, process steps 1 and 2 are first con used. It is above 130°C. ducted. Thereafter, the article, wet with toluene, is Metal being coated with aluminum acquires an adhe immersed into the molten pretreatment electrolyte 20 sive coating which is very pure and therefore bright like bath of 80 to 100°C bath temperature, consisting, e.g., silver, exceptionally ductile and corrosion-resistant. of a 1:1 mixture of NaAl(CH), and KIAl(CH), This coating is produced in the absence of oxygen and and is anodically stressed for a short period in order to moisture as well as corrosive media, and thus does not loosen and remove the surface film and scale. Subse contain interfering intermediate layers. The thickness quently, the article is immersed, wet with pretreatment 25 of the electroplated coating is normally in the range of electrolyte, directly into the aluminizing bath, under about 10 to 30 microns. Due to these advantageous inert gas. (N2), and the cathodic aluminizing electro characteristics, it is called "galvano-aluminum." Be plating process is conducted, accompanied by elec cause of its high degree of purity of at least 99.99% trode agitation. aluminum, this galvano-aluminum always provides, Besides these surface pretreatment methods, one can 30 regardless of the peculiarities of the base material of apply methods which produce bare surfaces, free of the molded bodies and structural components, a high surface films, in other ways and which permit a mois degree of corrosion protection and a silver-bright, very ture-free immersion of the article into the aluminizing decorative appearance; hence it represents a true sur bath, such as structural components freshly machined face finish. This applies equally for beryllium, magne under oil, from solid material, that can be placed into 35 sium, titanium and zinc as well as for aluminum arti the aluminizing bath, following PER degreasing and cles. In addition, galvano-aluminum layers have very washing in toluene. good electrical surface conductivity, superior ultra According to the invention, the aluminization by sonic weldability due to their high ductility (20 kg of electroplating can be carried out with aprotic organo force/mmHV; equal to 200 Newton/mmHV), and aluminum electrolyte media, free of molecular oxygen 40 high reflectivity after burnishing or polishing. The high and water, preferably with electrolytes containing an ductility of the galvano-aluminum lends the structural aluminum alkyl. The use of special current and elec components of high strength, hard materials, particu trolysis conditions, particularly pulsed current with larly beryllium, magnesium and titanium alloys, a good polarity reversal cycles, may have a favorable influence sliding surface and a metal-to-metal sealability with upon the type of deposition of the electro-deposited 45 appropriate contact pressure. aluminum. The particular type of electro-crystallinity Furthermore, the components electroplated with produces a dull, glare-free surface. Normally, the depo aluminum have excellent properties for anodizing. This sition current density is in the range of 10-20 mA/cm. expands, the possibilities for surface finishing the gal Good electrodeposition can be obtained even up to 60 vano-aluminum-coated light-metal articles to a particu mA/cm. At higher current densities, an intensive 50 larly large degree. In addition to the corrosion protec movement of the cathode or of the electrolyte is prefer tion resulting from the silver-bright but relatively soft able, particularly for the dissipation of the Joulean heat galvano-aluminum plating there is also the corrosion which is released. protection by the crystal-clear, transparent and wear on principle, all organoaluminum electroplating elec resistant galvano-aluminum eloxation layer which is trolytes which correspond to the following general 55 surprisingly hard (over 4000N/mmHV) and which formula are suitable for carrying out the method ac protects the surfaces of the article against mechanical damage. The protective layers which are produced by cording to the present invention: anodic exposure of the galvano-aluminum coating in MXARRR -- solvent the eloxation (anodizing) baths (which are known per 60 se) in almost any desired layer thickness, owe their where M can be Nat, K*, Rb", Cs or a quanternary particular characteristics to the high purity of the gal onium ion with N, P, As or Sb as the central atom or a vano-aluminum. These characteristics are: exception tertiary onium ion with S, Se or Te as the central atom; ally crystal-clear transparency, high homogeneity and X is preferably F or CI but also Brand I, CN, N. hardness of the eloxal layer, good insulating properties or 4CSO); n is greater than unity, preferably 2 to 3; 65 and heat conductivity, the clear-color dye-ability and and R is always an organyl radical, preferably an alkyl stainability of the eloxal layers produced in GS baths, radical, more particularly ethyl or methyl radical; R' and very good hardening (or sealing) characteristics of may be the same as R, but may also be an hydride (H) the galvano-aluminum eloxal layers from GS and GX radical or an halide (F, Cl") or other monovalent eloxation baths. 3,969,195 10 In accordance with a preferred embodiment of the ductile, adherent and gently force-transmitting auxil invention, the aluminum coated articles are anodized iary agent, which makes other auxiliary substances of as an after-treatment. When the above-indicated, spe the conventional kind unnecessary because it provides cific requirements for the current and the electrolyte a dry sliding and lubricating film and thereby increases for the deposition of the aluminum are adhered to, a the useful tool life considerably, but constitutes at the dense and perfect anodic oxidation is obtained with the same time an effective surface finish which provides methods commonly used in industry. The resulting GS corrosion protection for the normally less noble sub eloxal layers can subsequently be dyed and solidified strate metal, imparts higher electric conductivity, ex (sealed)...... cellent weldability and solderability and presents a If dyeing is not desired, the solidification (sealing) is 10 metallic, bright and possibly brilliant decorative ap carried out with boiling water above 95°C, or with pearance. superheated steam...... Depending on the peculiarity of the electroplated The crystal-clear eloxal layers obtained when the metal applied, the following surface properties or sur article is pretreated and electroplated according to the face finishing possibilities can be listed in addition to method of the present invention are characterized, 5 the properties which are effective for forming, namely, particularly, by extreme hardness (400 kg/mmHV; electroplated aluminum, which is especially ductile 4000 Newton/mmHV) and wear-resistance. They can from room temperature to 660°C; be dyed with color-clearness and be printed on. They electroplated zinc, which is especially ductile from also have good thermal conductivity with a high insula 80° to 160°C; - tion resistance and a high corrosion-protection capabil 20 electroplated cadmium, which is especially ductile ity and can readily be polished by mechanical means. from room temperature to 321°C; In some cases, when corrosion protection is desired electroplated indium, which is especially ductile from irrespective of the decorative surface appearance, yel room temperature to 156°C; lowish or greenish protective layers can be produced in where approximately the following order applies re the galvano-aluminum coating by conventional chemi 25 garding softness of the electroplated metals: cal oxidation methods, such as, for instance, the Ind-CdZAl-Zn, chromatizing method. In other instances, for example and the bondability to the substrate metal in the form with titanium and titanium alloys, a particularly hard ing process (in the manner of compression or friction titanium-aluminide layer can be produced by diffusing welding) increases from zinc to indium to cadmium to in the electro-deposited aluminum layer. . . . 30 aluminum. Some of the special characteristics of aluminum Due to its high purity of over 99.99%, electroplated which are responsible for its wide technical application aluminum exhibits a strong corrosion protection effect, can thus be applied on surfaces of other metal articles. which can be enhanced further by anodic oxidation to For example, the dyeing properties (inherent only to formeloxal layers. These can be sealed, are insulating, aluminum) of the layers which can be produced by 35 can be dyed and printed, and are extremely hard and anodizing in GS baths, can be applied to other metals abrasion resistant. The electroplated aluminum layer as and to the gray or black eloxalized aluminum alloys. well as the electroplated aluminum eloxal layer makes The surface oxide-layers of beryllium, magnesium, a good adhesion base for paints and adhesives. It has a titanium and zinc articles cannot be dyed. silver-bright appearance, can be polished and bur A particular advantage of the present invention lies. 40 nished and has very good thermal and electrical prop in the face that light metals and alloys, particularly erties, excellent ultrasonic weldability and solderabil beryllium and magnesium and high-alloy aluminum ity. Good bonding possibilities by friction and compres which are particularly suitable for mold-casting, extru ision welding exist. It is highly suited for subsequent sion or die casting procedures because of their high diffusion processes (aluminide formation). strength and good machinability, or their excellent 45 Electroplated zinc has a metallic, bright appearance workability, can be provided with the excellent surface and also exhibits a good corrosion protection effect, characteristics of high-purity aluminum, the galvano which can be enhanced further by chemical oxidation, aluminum coating. A coating according to our inven for instance, by chromatizing. The zinc layer consti tion provides not only durable corrosion protection but tutes a good adhesion base for paints and lacquers, and very often makes possible the application of these met 50 is well suited for soldering. als in technology. Thus, for example, magnesium and Electroplated cadmium is distinguished particularly magnesium alloys could not heretofore be electro by a good corrosion protection effect for ferrous mate plated. rials. It forms a useful adhesion base for paints and A further, very particular advantage of the invention lacquers and is highly suited for soldering. It is also resides in the fact that the electroplated metals exhibit 55 suitable for ultrasonic welding. As it is suited as a base a very effective sliding and lubricating effect. Electro for chromium plating, protection of the rather soft plated aluminum has a Vickers hardness of less than cadmium against mechanical damage being best 200 N/mmHV and is therefore more than three times brought about by chromium plating, and at the same more ductile (or softer) than gold. Contaminating lu time, excellent protection against corrosion is ob bricants and forming additives become unnecessary. If 60 tained. materials electroplated according to the invention with Electroplating with indium is particularly well suited aluminum, zinc, cadmium or indium are used, the ser for friction and compression welding. vice life of the tools for the drawing, pressing, emboss It should also be emphasized that the galvano ing and stamping operations is considerably increased, aluminum deposition may be done in the complete by up to 50%. 65 absence of hydrogen. This factor is of paticular impor The coating of electroplated metal therefore not only tance among the light metal metals being discussed makes possible and facilitates the mechanical forming here; e.g., titanium absorbs into its metal lattice hydro in the fabrication process mentioned above as a soft, gen present in statu nascendi, thus changing its me 3,969,195 11 12 chanical properites in an adverse manner. The hydro and non-ferrous metal materials such as, for instance, gen embrittlement and stress corrosion induced brass or copper, may also be made of ferrous materials. thereby cannot occur in electroplated materials; this is In particular, sections of steel strip can be coated on an extremely important advantage of the galvano both sides with electrodeposited aluminum, zinc, cad aluminum coating. The metal deposits occurring from mium or indium. aqueous electroplating baths are almost always accom Aluminum has the greatest importance among the panied by a rather strong hydrogen evolution, which at electroplated metals mentioned because of its special the same time reduces the cathode efficiency. The properties and its favorable melting point of 660°C, galvano-aluminum deposition takes place without gen and, not least, because of its low price. For this reason, eration of hydrogen with a cathode efficiency of almost 10 the advantages and possible applications for mechani 100% of theoretical. cal forming processes and surface finishing attending The method of the invention can be used for coating the electrodeposited aluminum coating will be illus or for surface finishing various molded bodies of base, trated in the following examples; the same or similar oxygen-affinitive metals. Surface protection with a procedures are also possible with the other electro desirable decorative appearance may be obtained; this 5 plated metals and lead to analogous results. is important particularly for components used in den The invention will be described in greater detail in tistry, electronics, in the automobile industry, as well as the following Examples: in air and space vehicles. Due to its high ductility, the galvano-aluminum plating can also be used as a sliding EXAMPLE and lubricating film. Furthermore, surface brightness 20 Electro-Aluminizing Of Beryllium Discs (luster) can be provided by mechanical means, as for 2 mm-thick beryllium discs of 40 mm diameter are example by buffing, or also by barrel polishing. The arranged in a cathode frame consisting of titanium, shiny surfaces can be protected against mechanical fixed at the lateral edge with small dovetail pins, and damage by subsequent anodizing. A further advantage contacted. Following PER vapor-degreasing and dry of the high ductility of the aluminum coating is also 25 ing, the arrangement is placed, wetted with toluene, found in the bonding technique of ultrasonic welding. into the aluminumizing electrolyte comprising trimeth The galvano-aluminum eloxation layers, make it possi yl-benzylammonium-hexaethylmonochlorodialanate ble to finish the surface of handles, front panels, sub strates and die castings. Moreover, the galvano with an excess of 0.2 mol of Al-triethyl, in toluene (1:3) aluminum eloxation layer forms an ideally adherable and is anodically plated at 80°C for 15 min. with inten base on the surface of the light metal articles for paint sive agitation of the electrolyte media. Then the ing, plastic coating, cementing and impregnating. . polarity is reversed and, at a current density of 11 For continuously operating aluminizing installations, mA/cm, accompanied by further electrolyte agitation, for instance, for wire and strip run-through installa a galvano-aluminum layer of about 15 micron thickness tions, the procedures of electropolishing, known perse, 35 is deposited in 90 min. The discs are removed from the (there are available electrolytes for ferrous materials, aluminizing cell, the adhering electrolyte is rinsed off non-ferrous metals and aluminum materials, and oth the discs with toluene, which are then briefly dipped ers) with subsequent intensive washing, water displace into TRINORM 'Al' and washed in water, and there ment (by means of dewatering fluids) and wetting with after dried with acetone. The galvano-aluminum coat toluene can also be used to advantage for, producing 40 ing has a bright fine-crystalline appearance. and retaining a pure, bare surface which is also pro The beryllium material is coated with tightly adher tected against renewed oxidation. Particularly in fer ing, galvano-aluminum. The galvano-aluminum layer rous materials, the so-called surface cleaning with cop may be anodized, and further surface refining such as per flash (less than 0.5 micron of copper layer) in an dyeing, marking, printing, lettering, cementing, etc. aqueous system, with washing and water displacement, 45 may be carried out. may be employed in addition to the methods described above. For the organophilic beryllium, magnesium, EXAMPLE 2 zinc and aluminum materials, the surface pretreatment Electro-Aluminizing, Anodizing And Dyeing Of Ber by anodic loading in aprotic, oxygen- and water-free yllium Blocks organometallic, perferably organo-aluminum electro 50 In a titanium cathode frame, four beryllium blocks lytic media, has been found to be particularly suited. (6x6X16 mm) are fixed above their square end faces The layer thickness to be chosen for the electro with two titanium contact tips and hydraulically sur plated aluminum depends primarily on the intended face-treated with 70 micron fine electro-corundum extent of deforming of the substrate metal, and second particles suspended in a 1:1 mixture of paraffin oil-sili arily on the desired thickness of the eloxal layer. Also 55 cone oil at a jet pressure of 6 atm. Subsequently, they the hardness or ductility, respectively, of the substrate are washed at once in a PER immersion bath, de and the speed of forming have an influence on the greased in a PER vapor bath and rinsed in toluene. Wet required or optimum layer thickness of the electro with toluene, the beryllium blocks are lowered under plated coating. dry nitrogen gas into the aluminizing cell, the electro In case the electroplated coating is needed only as 60 lyte of which is Na (CH)AlFAl(CH3) 3.4 the auxiliary forming agent and its presence on the CHCH3. At an electrolyte bath temperature of surface of the formed part is undesirable, the coating 95-100°C, electro-deposition of aluminum takes place can be removed again by mechanaical, chemical or under mechanical cathode agitation, with a current electrochemical means. density of about 10 mA/cm. After 3 hours, with a By the method according to the invention, drawn, 65 polarity reversal cycle of 4:1, a galvano-aluminum layer pressed, embossed and stamped parts and parts pro of about 30 microns thickness is plated on the surface duced by squeezing, rolling or explosion methods, of the blocks. It is highly adherent and homogeneous. which heretofore have been made preferably of light The adhering electrolyte is removed from the blocks by 3,969,195 13 14 washing in toluene, blow-drying and brief immersion rinsing with toluene in an ultrasonic bath, the toluene into TRINORM Al. moistened parts are subjected in a protective nitrogen With the same arrangement of the beryllium blocks atmosphere to surface pre-treatment. The electrolyte in the titanium frame, the anodizing process is carried bath was molten (90-100°C) 50% NaAl(CH3) and out immediately thereafter at 18°C in a GS (direct-cur 5 50% KAl(CHs). With the electrolyte circulated by rent, sulphuric acid) anodizing bath. Within 35 min stirring, the surface of the electron metal bars is anodi utes, a colorless, crystal-clear galvano-Al-eloxation cally pre-treated for 15 min. at a current density of 18 layer of approximately 12 microns thickness grows on mA/cm, and a surface film about 2 microns thick of the surface. . magnesium is removed, together with the oxide surface Prior to solidification of the eloxal layer in boiling 10 layer. A nickel screen serves as the cathode. With a deionized water for about 30 minutes, a coated block is favorable arrangement of the pre-treatment bath, im dyed in a staining solution of 5 g/liter of a dye known as mediately adjacent to the aluminizing bath, the frame Aluminum-True-Red B3LW (available from SANDOZ AG, Basel) for 10 min. at room temperature. While the and work pieces, still wet with electrolyte, can be di uncoated beryllium blocks have a blue-grey surface 15 rectly lowered, under protective nitrogen gas, into the color, the unstained anodized blocks, coated with a aluminizing cell. Otherwise, the frame and the now galvanoaluminum - eloxation layer, have a matte silver metallically-bare electron metal parts are rinsed with bright hue. toluene and the toluene-wetted parts are transferred to In the same manner which applies to pure beryllium, the aluminizing bath. molded articles of beryllium alloys, particularly high 20 In an 80°C plating electrolyte bath of NaI(CH)Al percentage beryllium-aluminum alloys with 48 to 52% FAl(CHs)a). 4.0 CHCH, the parts are coated, over beryllium content, can be coated and stained or dyed, a period of 2.5 hours, with a galvano-Al layer about 25 printed-on or lettered. Suitable dyes are, for example, microns thick. The process is conducted at a cathode the Aluprint dyes available from SANDOZAG, Basel. agitation rate of 6 cm/sec and 12 mA/cm current den 25 sity by means of a pulse current (5:1) and 25 Hz. After EXAMPLE 3 spraying with toluene, rinsing with hot water and dip Electro-Aluminum-Coating Of Cylinders Of Magne ping for a few seconds in TRINORM Al, the aluminized sium Alloy electron bars are given an anodizing treatment in a GS Two cylindrical pieces of 70 mm diameter and 100 bath at 18°C for 20 min. The resulting eloxation layer, mm length consisting of magnesium alloy are attached 30 fully transparent and about 8 microns thick, is dyed for in a rotating holder of Ti rods, and their surfaces 5 min. in a 60°C SANDOZ staining bath with Al-True treated by means of pressure jets with 80 micron glass Gold L(2 g/l) to a gold color and is solidified in boiling beads in PER at a jet pressure of 6 atm. After spraying water for 30 min. with hot PER and, finally, PER vapor, the still-hot parts, together with the rotating holder, are immedi 35 EXAMPLE 5 ately lowered into the 100°C aluminizing bath and Electro-Aluminizing, Anodizing, Printing And Dye aluminized between two Alanode plates (space about ing Of Die-Cast Zinc Articles - 15 cm) with a cathode movement rate of 10 cm/sec and Toy cars (approx. 60X28X20 mm) of die-cast zinc rotation of the parts. The current source is a pulse alloy, e.g., DG ZnAl4 or DG ZnAl4Cu1, are disposed generator which, at a cathode?anode polarity reversal 40 at a distance of 20 mm in a frame with two titanium cycle of 4:1 (rectified value of cathode current, 12A; of point-holders and are surface-treated by means of pres the anode current, 3 A) and 50 Hz. deposition fre sure jets with electro-corundum (70 microns) in vis quency, at about 5V deposition voltage (amplitude cous paraffin oil at a jet pressure of 5 atm. After wash height), applies an average current density of about 15 ing in PER, degreasing in PER vapor and rinsing in mA/cm to the objects to be aluminized. In two hours 45 of plating time, a sliver-bright, pore-free and tightly toluene, the toluene-wetted frame with the cars is adhering galvano-aluminum coating about 30 microns transferred under N, gas into the aluminizing electro thick is obtained on the cylinder surface. The cathode lyte. With cathode agitation of 10 cm/sec, the die-cast frame, withdrawn in a dry nitrogen atmosphere from zinc toy cars are coated on their outer surfaces under the aluminizing bath, together with the coated magne 50 the current conditions stated in Example 3, resulting in sium cylinders, is sprayed with toluene and thus an approximately 30 micron thick plated galvano-Al cleansed of the adhering electrolyte. In the same man layer. ner, any desired magnesium materials which are fre One half of the number of Zn die-cast parts are pol quently used because they are easy to work by casting, ished by means of a barrel polishing with steel balls of 55 2 mm diameter, in a rotating polyethylene barrel and, can be provided with an aluminum layer, which further subsequently, anodized in a GS bath of 15°C; the other increases the usefulness of these light metals. half is directly subjected to anodizing without polish EXAMPLE 4 ing. Electro-Aluminizing, Anodizing And Staining Of For carrying out the anodizing treatment, the interior Bars Of Electron Metal, Containing 90% Or More Of 60 surfaces of the toy cars are coated with a masking paint Magnesium And Minor Amounts Of Aluminum, Zinc, that resists sulfuric acid and, thereafter, the outer area Manganese, Copper And Silicon is coated with an eloxation layer of 15 to 20 micron In a 300X500 mm titanium cathode frame of an 80 thickness. The well-washed eloxation surfaces are then liter aluminizing cell, 8 pieces of electron metal bars of marked and printed with Alu-print "Black' color-paste 135X26X16 mm, with longitudinal slots of appr. 1 mm 65 (SANDOZAG, Basel) and thereafter stained for 5 min. width and 0.5 mm depth, are fixed in two rows by at room temperature in a SANDOZ color bath of Al means of titanium point-contacts over the cross-sec Blue LLW (3.5 g/l) and subsequently solidified in boil tional area. After intensive PER vapor degreasing and ing water of pH 5.5 for 30 min. 3.969, 95 1S 16 In this manner, shiny as well as glare-free mat, wear uene-moistened parts are then electroplated with alu resistant, printed and stained galvano-Al eloxation minum for 3 hours in a 100°C aluminizing electrolyte layer, surfaces are obtained. bath of triethylphenyl ammonium-chloride and 2,2 aluminum-triethyl, dissolved in an equal volume of EXAMPLE 6 5 toluene, at a cathode movement of 15 cm/sec and an Electro-Aluminizing And Anodizing Treatment. Of aluminum anode spacing of 5 cm with a current density Hollow Cylinders Of Malleable Aluminum Alloys of 10 mA/cm. With the aid of threaded titanium supporting mem bers, 5 columns each comprising 8 hollow cylinders (20 EXAMPLE 8 mm outside diameter, 54 mm long, 1.5 mm thick) of an 10 Electro-Aluminizing And Masked Anodizing. Treat aluminum alloy (AIZnCu 1.5 F53) are fixed upon one ment And Dyeing Of Aluminum Sheets another and simultaneously contacted in the frame of Six sheets (100X 50 x 2 mm) of 99.5% pure alumi an 80-liter aluminum electroplating cell. In the pres num, are fixed in an insulated titanium frame structure surerjet apparatus, the parts are surface-treated while in two rows above each other by means of Tipoint being rotated with 6 atm.jet of micron corundum pow- 15 contacts, and simultaneously contacted. The surfaces der in paraffin-silicone oil. The parts, freshly machined, are degreased by etching with diluted caustic soda and are delivered wetted with oil, and can be immediately are given a preliminary cleaning. After vigorous rinsing treated, so that only a surface layer a few microns thick in water, the water is removed by dipping into acetone need be removed. After PER washing, PER vapor degreasing and rins- 20 and thereafter toluene, then the Ti support-structure ing in toluene under ultrasonic action (about 5 min with the sheets, is immersed, under N gas, into the total), the pretreated cylinders, wet with toluene, are electrolyte of NaI(CH)AlFAl(CHs). 3.0 toluene. placed, via an inert-gas lock, into the aluminum elec In order to remove the oxide-hydroxide outer layer trolyte bath. At a cathode movement of about 13 that has developed through contact of the aluminum cm/sec, the aluminizing is carried out for 1.5 hours, 25 with water, the sheets are anodically charged (i.e., with a pulsed current of average current density of 12 - electrically pre-treated by serving as the anode of a mA/cm and a polarity-reversal cycle of 4:1, at 50 Hz. circuit) for 10 min. The current density is 30 mA/cm. The galvano-Al layer thickness is about 15 microns and The Ti structure is moved back and forth at 15 cm/sec; has a fine-grained silver-bright appearance. the electrolyte (at 90) is mechanically stirred. The The anodizing process is performed, after washing 30 oxide cover layer is thereby removed, together with a with toluene, dipping into TRINORM Al and rinsing in thin layer of aluminum. . water, in a GS bath of 18°C for 20 min. (17.5 V, 15 immediately thereafter and in the same electrolyte, mA/cm) and a crystal-clear eloxation layer of about 6 the now-metallically-bare surfaces are coated in 55 microns is obtained. The layer is solidified for 20 min. min. with a tightly-adhering galvano-Allayer about 20 in superheated steam of 110°C. 35 microns thick, employing polarity reversal with 20 High-purity aluminum and Raffinal, which are usu mA/cm average current density and the usual pulsed ally the purest aluminum types technically available, current conditions (see Example 6). Afterwashing with are too soft for most technical structural applications toluene, dipping in TRINORM Al and rinsing in water, and do not have enough mechanical strength. During drying is effected with the aid of acetone. attempts to machining them hanically by drilli 40 For anodizing only a portion of the surface, the rect milling,pus grinding to and1ning the like,mechanically they "smear' byand drilling warp. angular faces of the aluminized sheets are covered in Their use in manufacturing is limited, except for press selected areas with self-sealing, acid-resisting plastic ing, stamping and rolling processes. Among the alumi foil, cut in the shape of a design with cross-pieces 5 mm num alloys, such as, for example, Al-Mg,Al-Cu, Al-Si in width. The sheets are now anodized in a 15° GX and Al-Zn alloys which, due to their high strength, 45 (direct current, oxalate acid), bath for 30 min., and an good mechanical workability and plasticity through eloxation layer approximately 12 to 15 micron thick is hot-pressing, forging and casting, have attained sub produced on the exposed surface parts and edges. After stantial importance in automobile, ship and airplane thorough rinsing in water, the adhesive foil is pulled off, construction, the minor alloy constituents and impuri the sheets are again washed and the GX eloxation layer ties, specifically Si, Mn, Cu, Fe, Pb, cause particular 50 is dyed in a SANDOZ color bath Al-black MLW (10 difficulties during anodizing because, e.g., of reduced g/l) at 60°C for about 5 min. Finally, the eloxation hardness or their inherent (natural) color. As a result layers which are dyed black are solidified in boiling of the present invention, the same high-purity galvano water for a period of 30 min. aluminum electroplated coating which has the valuable The surface of the thus-partially anodized sheets is characteristics described above can be electroplated 55 not perfectly planar, because the surface of the eloxal onto such alloys. The technology of aluminum applica layer is at a higher plane than the surface of that por tions is considerably advanced thereby. tion of the galvano-aluminum layer which was under the masking foil. The depressions in the surface may be EXAMPLE 7 filled in as follows. Since eloxation layers are not at Electro-Aluminizing Of Die-cast Perforated Alumi- 60 tacked during the anodic surface pre-treating process num Plates in the aluminizing electrolyte, but a surface layer of the In a titanium frame structure, 3 perforated plates galvano-aluminum could well be removed, the afore (100 x 60 x 3 mm) of the aluminum alloy DG Al Sil2, described surface treatment can be repeated in the are fixedly disposed with Tipoint contacts above their electrolyte and, thereafter, the galvano-aluminum sur narrow edges, and surface-treated in a pressure-jet 65 face which was under the masking foil can be thickened apparatus at a jet pressure of 5 atm. with electro-corun up to the level of the GX eloxation surface by means of dum (SN 120) suspended in oil. The subsequent wash polarity reversal by electroplating additional aluminum ing and degreasing is done as in Example 6. The tol thereon. 3,969,195 17 18 In a pivoted titanium frame, cylindrical wobblers, EXAMPLE 9 provided with a longitudinal 7 mm diameter bore and Electro-Aluminizing Of Titanium Strip And Surface consisting of TiAV64 alloy, are arranged in 4 columns refining By Aluminum Diffusion of 8 pieces each, and surface pre-treated by means of Strip titanium, e.g., type CONTIMET 30 or 35, 160 pressure jets with silicon carbide (100 microns) in mm wide and 0.5 mm thick, is passed for surface pre FRIGEN 113 at a jet pressure of 8 atm. treatment and aluminizing on both sides through a strip Following PER washing and toluene-rinsing, the aluminum electroplating apparatus which operates wobblers are placed into the aluminizing bath and are continuously. coated with an approximately 15 micron galvano The surface pre-treatment of the incoming titanium 10 aluminum layer, accompanied by reciprocal movement strip may be done by means of pressure jets with 100 of the frame and rotation of the columns. micron silicon carbide particles suspended in trichlor Subsequently, they are intensively anodized (under trifluorethane (FRIGEN 113) or a higher-boiling fluo conditions as described above) and dyed in a SANDOZ ro-hydrocarbon at a jet pressure of 10 atm. with jet color bath of Al-Blue LLW (2 g/l) at room temperature nozzles being directed to both sides of the strip, and 15 for 2.5 min. The galvano-aluminum eloxation-layer under nitrogen gas. Alternatively, it may be done by surface is solidified in boiling water for 30 min. and has means of liquid-drop impact erosion with FRIGEN i 13 an homogeneous, light-blue and glare-free appearance. (density of 1.58 g/ml) or a liquid perfluoro-hydrocar This is particularly important when a uniform, deco bon of greater density. In the first case, following sur rative surface appearance is required for an article face pre-treatment with FRIGEN 113, the 'strip is 20 fabricated of aluminum alloy, brass and titanium com washed free from particles and - in both instances - ponents. . . . . dried under nitrogen gas. The metallically-bare tita nium strip then enters an aluminizing electroplating EXAMPLE 1 cell containing a suitable electrolyte and is coated on Punch-Pressed Parts of Brass Sheet Coated On Both each side with about a 10 micron layer of galvano alu 25 Sides With Electroplated Aluminum minum at a maximum current density of 60 mA/cm A piece of brass strip 70 mm wide and 0.5 mm thick within a passage time of 10 min. To realize this rela is surface-treated by etching for 30 seconds in a phos tively high deposition rate, the cathode-anode spacing phoric-acid containing etching solution, which is com is reduced to 10 mm and the electrolyte liquidis rapidly mercially available, for instance, from Schering AG, as pumped-over in counter current flow between the tita 30 TRINORM Fe. Then it is thoroughly washed with wa nium strip (serving as the cathode) and both aluminum ter, cathodically degreased in an alkaline or cyano anodes...... alkaline bath (commercially available as UNAR 58 or The coated strip is rinsed with toluene and dried, and Degreasing Bath NORMAL) for about 20 seconds and the galvano-aluminum, in a loosely wound state, is pickled in 10-percent sulfuric acid. After intensive diffused at 600°C to a depth 5 to 10 microns in two 35 rinsing with deionized water for about 1 minute, the hours. - adhering water is displaced by immersing the brass The surface pre-treatment, aluminizing and diffusion sheet strip in a dewatering bath (dewatering fluid com are conducted in the absence of hydrogen. mercially available, for instance, as HAKUDREN), and By analogy, the titanium alloys which increasingly the dry strip is immediately immersed in toluene, where gain significance in turbine and motor construction, in 40 any residual dewatering fluid is removed under the rocket and reactor technology as well as in aircraft action of ultrasonic vibration. construction, can be surface-refined. In the technically Still wet with toluene, the brass strip then is placed in important titanium alloys, aluminum is the alloying the aluminizing cell and is coated at a bath temperature component present in the greatest amount, e.g.: of 70 to 90°C and with the electrolyte comprising one 45 part (CH3)3(C6H5)N Cl, 2.2 parts of Al (C2H5), and Ti Al Mo 8-1-1 7.5-8.5% Al, 4 parts of CHCHs, circulated by pumping, in an inert Ti Al Mo 74 6.5-7.3% Al, atmosphere (N, or Ar) free of air and moisture, be Ti Al 64 5.75-6.75% A1, tween Raffinal plate electrodes (electrode spacing ap Ti Al Sn Zr Mo 6-2-4-2 5.5-6.5% A1, proximately 10 mm). Both sides of the strip are electro 50 plated with an aluminum coating about 30 microns since aluminum increases the strength of the titanium. thick. Depending on the motion of the electrolyte, According to the method of the invention, the usually current densities of up to 0.04 Alcm with only a few readily workable, unalloyed titanium types, can now be volts of bath voltage, and deposition rates of up to coated with galvano-aluminum. The diffusion of alumi about 40 microns per hour can be obtained. The elec num into the surfaces of the article produces particu 55 troplated aluminum layer has a very fine-grained, sil larly hard titanium-aluminum alloys. Sheets of titanium ver-bright appearance and adheres very well to the used for the construction of containers and for air-craft brass strip. : can thus be covered with a harder, wear-resistant sur From the brass strip, retaining ring parts with a face which has better heat resistance. Electroplated i0-mm deep profile of 52 mm outside diameter and 22 galvano-aluminum and galvano-aluminum eloxation 60 mm inside diameter are made on a punch press in one layers on titanium surfaces increase the protection operation. The electroplated aluminum withstands the against corrosion, particularly against salt water, and partially complicated forming process without the for provide a functional and decorative surface refining of mation of cracks and has assumed a shiny appearance the steel-hard light metal. at the heavily deformed portions. At the stamping 65 edges, the shaping tool has pulled down the electro EXAMPLE 10 plated aluminum over the height of the edge, so that Electro-Aluminizing, Anodizing And Dyeing Of Tita the brass is no longer visible. The high ductility and the nium Ti Alloy Wobblers : good thermal conductivity of the electroplated alumi 3,969,195 19 20 num make possible a short cycling time of the stamping As a result of the electroplating of the pre-treated operation. strip, the punched and cut edges are coated so well with By means of hydraulically jetting with glass spheres electroplated aluminum, i.e., covered over, that practi of about 0.1 to 0.6 mm diameter, the electroplated cally no rust forms. The previously shiny aluminum aluminum layer can be hammered smoooth and bur surface appears merely spotty. This, too, can be nished prior to stamping. After deformation, the parts avoided by a previously applied eloxal layer of 1 to 3 exhibit a silver-bright luster on all sides. If the stamped micron thickness. edges are well coated with electroplated aiurninum (if necessary, the stamped edges can also be protected EXAMPLE 1.4 with a resistant lacquer) the parts can be eloxized in a O Depth Measurements For Testing The Elongation GS (d-c sulfuric acid) bath to a thickness of about 7 Behavior Of Steel Strip Coated With Electroplated microns and, if desired, can be printed, or stained with Aluminum a clear stain in boiling water for 20 minutes. From the steel strip prepared according to Example 12, coated on both sides with electroplated aluminum, EXAMPLE 2 15 60 mm wide and 0.15 mm thick, pieces 75 mm long are Punch-Pressed Parts Of Sheet Steel Coated On Both cut and used for the depth measurement according to Sides With Electroplated Aluminum Erichsen (DIN 50101). The measurements are carried A steel strip (60 mm wide by 0.15 mm thickness and out with a sphere of 20 mm diameter. comprising 0.33% Mn, 0.07% C, 0.04% Al, 0.023% S, In all test pieces, depressions between 8.5 and 9.0 0.017% P, remainder Fe) is freed on both sides from its 20 mm are measured and smooth cracks without separa thin oxide or scale layer by hydraulic jetting at 6 atm. tion from the steel base were observed. All values gauge with corundum powder (80 micron particle di therefore met the specified value for deep-drawing ameter) in oil. The thin strip rests alternatingly on a flat quality of the steel strip. steel support during this process. EXAMPLE 15 The metallic, bare steel strip protected against re 25 newed oxidation and hydration by an oil film, is Deep-Drawing Of Shells Of Cold-Rolled Strip Coated cleaned by washing in liquid perchlorethylene and de With Electroplated Aluminum Or Zinc greasing in perchlorethylene vapor and is immediately Cylindrical shells of several millimeters to several centimeters inside diameter are customarily pressed or placed in toluene, where residual perchlorethylene is 30 deep-drawn from brass, copper or aluminum materials. removed by ultrasonic action. The bare strip, still wet In order to attain greater strength or thinner walls, with toluene, is then introduced into the aluminizing ferrous materials (steels) have also been used, but the cell and coated in a vigorously agitated electrolyte (one stronger material poses greater fabrication difficulties part NaF, 2 parts Al(CHs), 3.5 parts toluene) at a and causes more tool wear. With auxiliary forming bath temperature of 80-100°C, applying a pulsed cur 35 agents, the deep-drawing is made considerably easier rent (50 Hz, current density 0.015 A/cm, anodic-cath and technical advantages can be obtained, such as odic loading ration of 1:5) with about 20 microns of improvement of the drawing properties of the base electroplated aluminum. A silver-bright, finely crystal material, excellent dry-lubrication film, longer tool life, line, well-adhering electroplated aluminum layer is elimination of intermediate annealing, working with obtained, which allows a stamping process to be per 40 thinner walls, and others. formed extremely easily and rapidly. Metals electroplated in accordance with this inven Instead of the above-mentioned anhydrons surface tion are advantageous auxiliary forming agents, which pre-treatment, the steel strip can also be cleaned in a are particularly well suited, for the manufacture of phosphoric-acid containing bath (commercially avail shells by deep-drawing. For this purpose, a cold-rolled able as TRINORM Fe) by etching, and then pretreated 45 steel strip of 1 to 2 mm thickness is coated, preferably by cathodic degreasing with copper flash (less than 1 in a continuous process, with 10 to 30 microns of elec micron, preferably 0.3 to 0.5 micron of copper) in an troplated aluminum or zinc. The layer thickness of the alkaline bath. After washing with deionized water, the electroplated metal depends on the degree of forming strip is dried with a dewatering agent (Dewatering to which the substrate metal is to be subjected. The Fluid, commercially available, for instance, as HAKU 50 electroplated aluminum layer can be applied as de DREN), given an after-rinse in a toluene rinsing bath, scribed in Examples 11 and 12. With the same surface and the copper-preplated steel strip is aluminized by pretreatment, organo-zinc onium salt-complex electro electroplating as described above. lytes are used for the application of the electroplated From both steel strips coated with electroplated alu zinc layer, as for instance, can readily be prepared in minum, deep-profile set rings, flanged cups, hollow 55 accordance with German patent 1,200,817, i.e. profiled parts and the like can be produced in a particu one part (CH3)3(CHCH)NF; 2.2 parts of larly advantageous manner on a stamping press. Zn(CHs), 2.5 parts of CHCH, or EXAMPLE 13 one part (C2H5)4N]Cl; 2.2 parts of Zn(CH), Corrosion Behavior Of Punched And Cut Edges In 60 3.0 parts of CHCH, or Steel Strip Coated With Electroplated Aluminum one part (CH)4N] Cl; 2.2 parts of Zn(CH), From steel strip 0.15 mm thick, made according to 4.0 parts of CH Example 12 and coated on both sides with electro At electrolyte temperatures of between 60 and plated aluminum, 50 X 50 mm test samples are 100°C, these electrolytes have conductivity values in punched and provided on two opposite sides with eight 65 the range of 10 ohm cm and permit depositions cuts each, 15 mm long. The test samples are then sub employing cathode current densities of 0.005-0.02 jected to the tropical-climate test at 40°C and 100% air A/cm and bath voltages of 2-10 V (depending on the humidity for 400 hours. electrode spacing), a pure, silver-bright electroplated 3,969,195 21 22 zinc in compact form on the substrate metal surface, 5. The process of claim 4 in which said liquid com with good adhesion and free of hydrogen. prises a normally-liquid hydrocarbon, a halogenated From the electroplated aluminum- or zinc-coated hydrocarbon, a perhalogenated hydrocarbon, a silicon cold-rolled strip, circular discs of 20 to 25 mm diame oil, and mixtures thereof. ter are blanked out for deep-drawing shells of 16 mm 6. The process of claim 4 in which said liquid is a diameter and 56 mm length and are fabricated in 6 mixture of hydrocarbon and a silicone oil. drawing operations in a multiple-plunger press into the 7. The process of claim 1 in which the electroplating above-mentioned shells, which show a smooth to shiny electrolyte corresponds to the general formula: silver-bright appearance. 10 MX malR'R''R -- m solvent, EXAMPLE 16 where M may be Nat, K, Rb, Cs or a quaternary Stamped Parts Of Brass Sheet Coated On Both Sides onium ion with N, P, As or Sb as the central atom or a With Electroplated Indium tertiary onium ion with S, Se or Te as the central atom, After a surface pretreatment suited for the material, 15 X may be F, Cl, Br, I, CN, N or 4 (SO); n is a brass strip of 100 mm wide and 0.3 mm thick is greater than unity; and R is a monovalent organyl radi coated in organometallic electrolytic media, such as cal; R' may be the same as R, but may also be an hy are described in the German Pat. Nos. 1,236,208, dride (H) radical, a halide or other monovalent nega 1,170,658, 1,483,344 and 1,200,817 with a thin (10 to tive ion; R' is selected from the same class of radicals 20 microns) electroplated indium layer of 10 and sub 20 as is R' and on any specific molecule of the complex, sequently fabricated in a stamping press to make cov may be the same as or different from R'; and m (mols) ers, parts with annular grooves, shells or the like. is in the range of 0-5. Having thus described the invention, we claim: 8. The process of claim 1 in which said electroplating 1. A process for electroplating a metal article com is conducted employing a pulsed current and cyclical prising: polarity reversal. 25 9. The process of claim 8 in which the polarity rever a. eroding the surface of said article with finely sal is in a frequency range of about 10-200 Hz. divided abrasive particles suspended in an anhy 10. The process of claim 1 in which said article is drous aprotic liquid; and protected from exposure to moisture and an oxidizing b. electroplating said article in an aprotic organo atmosphere after said eroding and until said electro metal electroplating electrolyte free of water and 30 plating thereof. molecular oxygen. 11. A process for electroplating a metal article com 2. The process of claim 1 in which said article is prising: electroplated with aluminum, cadmium, indium or a, eroding the surface of said article with finely 2C, divided abrasive particles suspended in an anhy 3. The process of claim 1 in which said metal article 35 drous aprotic liquid; is aluminum, beryllium, hafnium, iron, steel, magne b. protecting said articles from exposure to moisture sium, niobium, tantalum, titanium, tungsten, vanadium, and an oxidizing atmosphere; and zinc or zirconium or alloys thereof. c. electroplating said article in an aprotic organo 4. The process of claim 1 which comprises hydrauli metal electroplating electrolyte free of water and cally jetting said liquid under high pressure against the 40 molecular oxygen. surface of said article. k k k k s

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