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Every C2/C3 gas cap I have ever replated has been zinc. I highly doubt any were cad. Can't speak for C1 but my guess would be zinc as well. After all, why would a supplier choose cad over zinc when given the choice by GM?
I took a look at the drawing for the gas cap p/n 3843576 and the specifications state : Parts marked "*" are to be cadmium or zinc plated per GM 4252-M code 20. Finish is to be as taken from plating bath.
The handle and inner and outer stampings all had the asterisk.
So that means the finish was optional in the design....it doesn't indicate what it was year to year or supplier to supplier.....
That is optional on the drawing, but the parts also had to be qualified as passing a corrosion test. Depending on the test specified, Cad may have been a default choice due to it being the only coating that would survive the corrosion test. I know the outfit I worked for did many underhood parts in Cad as it was the only way to pass the durability tests. Also remember in the 60's Cad was not touched by the thumb of the environmentalists until very late in the decade. The cost of CAD at that time was not really much of an issue.
Bill, do you think it could have been a clear zinc, thats the appearence that my nos 72 cap has.it is not the factory cap, but survived in a box for 30+ years.
New England chapter member, 63 Convert. 327/340- Chapter/Regional/national Top Flight, 72 coupe- chapter and regional Top Flight.
From the platers that I've talked to, there is a clear preference for cad clear over zinc. It's a better plating material, but both are acceptable.
Region VII Director (serving members in Arkansas, Kansas, Louisiana, Missouri, Oklahoma and Texas).
Original member of the Kansas City Chapter, est'd 07/11/1982.
Member: 1965 and 1966 National Judging Teams
Judging Chairman--Kansas City Chapter.
Co-Editor of the 1965 TIM and JG, 6th and 7th editions.
Generally the cad and zinc were both plated as a clear finish. Gold colored cad (and zinc) are the result of a wash subsequent to the plating process itself, although it is usually performed on the same line, just another tank. The gold irridite generally improved the corrosion resistance over the white natural finish of cad or zinc. the closer you get to the late 60's early 70's the more likely Zinc or tin plating, was used, with or without the gold post plating processing, depending on corrosion requirement.
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