Posted by Spence on Sunday, January 29, 2006 at 4:14PM :
Hi Dave,
All of the brake boosters that I have run across are as follows: Cast iron cylinder casting is either black or unpainted, (almost all were unpainted). The aluminum valve assembly is unpainted. The vacuum reservoir (where the large rubber diaphragm is located) is cadmium plated.
The cadmium plating on the one that I rebuilt for my 1955 C3PW had not withstood the test of time and was not very good. So I painted the whole thing Black. I thought about painting the reservoir silver, but silver paint does not resist rust very well. Perhaps if you were to use some self etching primer (NAPA has some good stuff in a rattle can) the silver paint would hold up better. The general problem with painting boosters, wheel cylinders and master cylinders is that brake fluid softens and removes the paint in short order. It is difficult to keep the paint in good condition if there are leaks or spills while bleeding. Perhaps this it the reason that you do not see paint of these components from the factory.
Hope that this helps answer your question.
Check out the new pages that Phil Street added to my webpag this morning on boosters at the link below. (Thanks Phil!)
Spence
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