A copule of us are ready to take a box of 66 and 67 L79 parts to the plating shop, mostly for cad plating. But...for some parts, like the choke spring housing an and the horn relay cover, the Judging Manual lists two types of plating cad or zinc. Anyway to know which is best choice if the Manual lists two? I know different vendors provided different finishes on parts but is the first one listed the most common? Any guidance is appreciated.
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John -
Re: plating of parts
JG's use term cad/zinc for two reasons: (1) original GM drawings for the part have been researched and it was found either/both finishes were called out as a supplier's choice, (2) there is controversy over which is the 'correct' finish based on judge's prior experience/knowledge and this is a compromise in wording. Either way, the choice is yours.
Now, zinc is easy to do and plentiful in terms of shops doing the work. It's finish is typically brighter than cad with a subtle blue undertone. Cad is a toxin (poison) and various regulatory bodies have been clamping down on it due to waste water effects. Some believe cad is a superior finish (durability) and it will have various degrees of yellow undertone.
On cad, there are two basic finishes you can get - bright or dull. The difference is the luster or 'shine' of the finished part. Straight from the tank, cad resembles lead and is definitely dull. You make it bright by polish/buff and/or using secondary operation(s) like tumbling in a mercury bath. The tumble work is usually done when the part has specific geometry that's difficult to buff/polish.
You CAN expect deduction(s) during concours judging if you get the wrong surface finish on the plated part (bright when originals were known to be dull, Etc.). But, within reason, it's possible to go back and fix this opps. Take a bright cad part and momentarily immerse it in a 50/50 solution of water and muriatic acid and you'll roughen the polished surface. Take a dull cap part and hit it with a SOFT wire wheel and you'll brighten it. Good luck! -
Re: plating of parts
Jack, Thanks for the info. It's knowledge like yours that makes the NCRS what it is!JohnComment
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