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Caring for Iron Alloy Objects

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Caring for Iron Alloy Objects Caring for Iron Alloy Objects 2017 Gerald R. Ford Conservation Center About Iron Alloy Objects composed of iron alloy are all around us, in the form of tools, weapons, hardware, containers, toys, kitchenware, ornaments, and art objects. The term “iron alloy” is used to describe a metal com- posed of iron which has been alloyed with another metal to change its properties. One well-known example is steel, which is iron that has been alloyed with carbon and other elements to increase its tensile strength. Iron alloy objects are more vulnerable to corrosion than other metals. They are often utilitarian objects, which means they are also more prone to getting dirty and being damaged from frequent handling. Han dl in g Using gloved hands, examine the struc- are often protected with paint coat- ture and surface of your object care- ings. Plating is a coating of one metal Inside this issue: fully, looking for cracks, weak areas, over another metal, and tin or zinc old repairs, and loose or missing parts. plating may be found on some objects Handling 1 To protect your object from scratching, created with thin sheets of iron. Zinc marking, or bumping, remove dangling plating is generally referred to as gal- Cleaning 2 necklaces, sharp rings, and protruding Waxing 3 belt buckles. It is important to determine if there Environmental Controls 5 are original decorative or protective Consulting a Conservator 6 surface finishes on the object before beginning to clean. Paint is a good ex- Additional Resources 6 ample of an organic decorative and protective coating material. Because they are so reactive, iron alloy objects Caring for Iron Alloy Objects vanizing. Another important type of alloy artifacts, particularly weapons, decorative and protective surface may have original patinated surfaces of sometimes applied to iron alloy items dark brown or dark blue. Brown pati- is a patina. A patina is a thin chemi- nation may easily be mistaken for rust. cally induced layer of relatively stable Organic coatings, plating, and pati- corrosion on the surface of an object. nated surface layers should not be re- Patina can also form over time from moved and could easily be ruined by use and handling and can give an ob- the cleaning procedures listed below. ject the “patina of age”. Many iron C l eanin g Thick layers of iron corrosion are highly (such as the “bluing” commonly expansive, disfiguring, and difficult to seen on weapons) reduce. The cleaning procedures listed Have paint on the surface or an or- below are not appropriate for heavily ganic coating corroded objects, as they are ineffec- tive on these surfaces. Are very heavily corroded In summary, the cleaning and waxing It can sometimes be difficult to deter- procedures below should not be car- mine the structural or surface condi- ried out on iron alloy objects that: tion of an object. If in doubt, please call a conservator. Are fragile or structurally unsound The cleaning and waxing of iron alloy Have plating of another metal over objects, while seemingly simple, is a the iron alloy (such as brass, process that requires careful thought bronze, silver, or gold) and attention to detail for a successful Have patination on the surface outcome. Before you begin the proc- ess, please review the section above to make sure your object can be safely cleaned and waxed without causing irreparable damage. Do not apply a wax coating to objects that will be used for food. Commercial cleaning products are gen- erally to be avoided, as many contain Page 2 corrosive chemicals such as ammonia, harsh abrasives, acids, or bases, which can permanently damage artifacts. surface. A sheet of polyethylene plastic Materials to Have on Hand They may also contain corrosion inhibi- can be placed on the sheet to help con- Clean towel and clean sheet tors that can cause unusual and tena- tain the mess during the cleaning proc- to create a padded work cious patterns of re-corrosion on your ess. Wear nitrile gloves to avoid con- surface object. The materials and techniques taminating both the object and your- Heavy polyethylene sheet- listed below have been tested and self. Oils, salts, and acids from your skin ing to protect the padded found to be safe and effective when can easily cause corrosion to metal sur- work surface used in a careful and sensitive manner. faces. Remove or mask out any non- Cotton swabs or pads, as Provide a clean, well-ventilated work metallic elements, such as wooden han- needed area for the cleaning and waxing proc- dles, with polyethylene plastic to pro- Nitrile gloves ess. Lay a towel down, followed by a tect these parts from cleaning materi- als. (recommended when work- clean sheet to create a padded work ing with mineral spirits) Mineral spirits Procedure Ultra fine (4/0) steel wool 2. Remove any waxy or oily accretions A penetrating lubricant prior to rust reduction. Thick areas of such as WD 40® or CRC 3- wax can be pushed off with the blunt 36® end of a bamboo skewer and thin layers Soft clean natural bristle can be lightly brushed with a natural brushes, such as haké, bristle brush or cotton swabs damp- watch, or paint brushes ened with mineral spirits. Rinse the Stiff natural bristle brushes brush in a small container of mineral and bamboo skewers, spirits or replace the cotton swabs as Apron or smock 1. Remove any loose dirt or dust by they become soiled. Clean the brush or brushing lightly with a soft brush or replace the swabs regularly to avoid Clear microcrystalline paste camel hair paintbrush. If brushes have scratching the surface with loosened wax, such as Renaissance© metal ferrules, cover them with tape to rust and accumulated grime. wax, or a clear hard paste wax available in hardware prevent them from scratching the ob- 3. To remove minor rust deposits, wet stores such as Behlens® ject. Do not use dusting cloths, as they small wads of 4/0 ultra fine steel wool paste wax. will not get into small crevices, and can with the penetrating lubricant and rub scratch artifacts if trapped grit is rubbed gently. If the corrosion is more tena- Clean natural bristle stip- over surfaces. If the artifact has soil cious, apply some of the lubricant with pling or stencil brushes, or that is firmly attached, a stiff paintbrush a brush and allow it to penetrate for up shoe buffing brushes, for or stippling brush may be needed. Vac- to 48 hours, keeping it covered with waxing and buffing uum away any residues, brushing the polyethylene sheeting to reduce evapo- Page 3 dust towards the vacuum nozzle. ration. After a sufficient amount of Caring for Iron Alloy Objects duced, clear any residues with clean mineral spirits using swab, brushes, or clean pieces of soft cotton rags. A clean soft brush may be used to remove any remaining residues from crevices or re- cessed design elements. Allow the arti- fact to air dry. Finally, remove the pro- tective wrap applied to non-metallic components. time has elapsed, the rust should be 5. Your piece is now ready for the appli- easier to rub away. Do not use bronze cation of a clean wax coating. The wax or tin wool in a mistaken attempt to re- used for this purpose is a clear micro- WARNING: When working duce potential abrasion. These materi- crystalline paste wax. Clean nitrile with solvents, be sure to follow als will actually leave a thin layer of cop- gloves should be worn to protect your all recommended safety pre- per alloy or tin on the surface that will hands and also avoid contaminating the cautions noted on the contain- increase the rate of corrosion through a object. Non-metallic elements such as ers. Mineral spirits are strong, process called galvanic interaction. wooden or ivory handles can also be reactive chemicals and their Never immerse an iron object in water, lightly waxed following the same direc- as it could begin rusting almost immedi- fumes can be harmful to your tions if they are approached with care. ately. health when not used as in- Only objects that have been properly structed. Nitrile and Neoprene 4. Once the corrosion has been re- cleaned and dried should be waxed. gloves offer the best protec- Waxing tion against mineral spirits and the solvents present in the 1. Apply a small amount of paste wax to previous coat, then buff immediately. wax mixture. Avoid using latex a clean stencil brush and rub thinly over 3. To maintain the coating, periodically gloves, as they do not offer the entire surface of the object, being adequate protection against careful to get complete coverage. Do the solvents used during this not apply too much- a little wax goes a long way. activity. Always be aware of the location of the nearest fire 2. Wait a minute or two and buff the extinguisher when working wax out with a clean stencil or shoe buffing brushes. Wax has a plate-like with flammable solvents and structure, and buffing helps to align and waxes. compress it into a more continuous and Page 4 protective coating. If you accidentally leave the unbuffed wax too long simply apply a little more wax to soften the dust the artifact with a soft haké brush, having a conservator apply a more du- checking each time for evidence of rust rable clear organic coating. Stable or- or corrosion. The wax should provide ganic coatings can provide up to twenty good protection for at least a year, de- years of protection and minimize re- pending on atmospheric and handling peated handling of objects.
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