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topic 6444

Cleaning stains on silver powdercoat


Noted the suggestion in letter #5106 to use a solution of stearic acid dissolved in xylene on the tin plate and wonder if this could also work on bright silver powdercoating finishes. The specific silver powdercoat I refer to is used on General Motors LT5 engines which exhibit very dark indelible discoloration spots when anti-freeze, brake fluid, engine degreasing gunks,or various other strong liquids make contact with the silver powdercoat surface. Likewise, use of abrasives, rubbing compound or polishing agents, causes dark discoloration of the silver. Topical application of benzene, lacquer thinner [linked by editor to product info at Amazon], mineral spirits, Acetone [linked by editor to product info at Amazon], bleach, soap and water, sandpaper, etc, have had no effect. If this can be reversed by any other means, I would be very grateful to hear the explanation.

Thank you


Randy S [last name deleted for privacy by Editor]
- Stoughton, Massachusetts


Randy, The bright silver powder-coating you describe gets it's look with the use of aluminum pigments. The pigment itself is usually at or near the surface of the coating and is subject to chemical reactions that can discolor or actually destroy the pigment. It's likely that discoloration on your coating cannot be reversed. To avoid further discoloration, you'll probably need to apply a clear-coat to protect the aluminum pigment.

Greg Walls
- Reading, Pennsylvania, USA

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