How to tint galvanizing to the color of cadmium
I am trying to run galvanized hard drawn through a spring coiler and the galvanized coating is giving me a nice shiny appearance. What I need it to be able to tint the material a color similar to cadmium plate QQ-P-416 [link by ed. to spec at Defense Logistics Agency, dla.mil] type II. If we can accomplish this with a coating that would be great. We also run this spring through a conveyor oven at 350 degrees. If there is a coating that can be applied to the wire before forming that then would turn a golden yellow upon heat..that would be acceptable. We are open to any additional ideasRobert Guard
Cadmium is the same silvery color as zinc. The golden yellow you are describing is due to a yellow chromate conversion coating, which can be applied to zinc as well as cadmium. But the problem is that it loses its protective value, and can dehydrate and slough off starting at about 150 degrees F. After baking at 350 degrees F it would have lost most of its value, although it might indeed be the color you are seeking. If it would be acceptable to chromate the finished parts after baking, I think you could get the color match you are looking for, and corrosion resistance as well.
Ted Mooney, P.E.
Pine Beach, New Jersey
I agree, deposit the conversion coating after heat treatment or it will turn a dirty deep brown. It may also not make it through the coiler in-tact. The best coatings are the old Allied Kelite line, now owned by Macdermid. Every color in the rainbow is available, though the non-standard ones are organic based.
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