I want to plate some CAD plated parts and was wonrdering if I should use self etching primer on them or not. Knowing that cad/zinc plating is sensitive to acids, is this a wise choice, or is it better to just paint directly over the cad plating? The parts I am looking to paint are some MM disk brake adapters. They are cad plated cast parts and are pretty rough so there is plenty for the paint to stick to but....or should I just use a non etching primer to be safe?

Adam,

Zinc plating for steel, like chem film for aluminum are often used as a primer for painting. I don't know if CAD falls into this same scenario. Typically these parts are painted shortly after being plated.

I've always thought the self etching primers had to be applied to clean, bare metal to actually "etch" into that metal.

Good luck with your car.

Bruce

Sorry for the confusion in terminology. I'm guessing that it's actually zinc plated with a yellow chromate finish since cadmium based plating is rarely used anymore. Not sure if that makes a difference or not.

You gotta remove the yellow chromate coating to get proper adhesion. This then poses a another question, is my new topcoat stronger than the chromate I'm removing?

This pic illustrates what happened when I scraped the bolt with my fingertip, not even my fingernail. Also, I did uses green DupliColor etching primer.

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Thanks Shin. I would expect that from a part with a shiny finish like that of plated bolts and such. In my case the brackets are cast and therefore have a rough finish. I was more curious whether a self etching primer would damage the plating, and cause the paint to flake off prematurely. I haven't decided what to do just yet but I'll probably just use a regular primer to be safe.