Greg -

Having worked in that environment for 38 years, I can assure you that suppliers, given the option of cad or zinc, used zinc, as it met the Engineering requirement at less cost; they could care less what it looked like as long as Engineering approved it.

 

John, you're probably right about that, cost would be a higher priority than appearance. If the part had zinc originally I would order zinc without question.

 

Greg,

The appearance is not an issue. The appearance of the finished product depends on the process and not the metal used. both zinc and cad can look exactly the same, depending on the process. After plating parts for many years, I still can not always tell the difference between zinc and cad. The people at the cad plating shop that I use for my radio cases say the same thing. Zinc does not have to be bright and shiny, that is a function of the brighteners and agitation that is used. Most Zinc done today is bright and shiny, because that is what most people want. This bright surface is accomplished buy using a brightener additive, rinsing the parts in a dilute nitric acid and then post treating with clear chromate. This imparts a slightly blue hue to the finished product. To get the dull silver surface that is used on most Corvette parts, you simply don't use a brightener additive and the part will be nice and dull. You have to maintain 2 separate tanks, since the brightener is in the plating solution. Some C1 Corvette parts had a slightly yellow-gold tone to them and this is accomplished by post-treatment in a yellow chromate dip. The longer the part sits in the dip, the more golden it becomes. The chromate was used to make the plated surface more durable. The chromate converts the top surface of the plating to either zinc dichromate or cadmium dichromate, whic is a much more durable surface than the plain plated metal.

While Zinc can be made to look like cad, it is almost impossible to get a cad finish to be bright and shiny, so if it is shiny, it is probably zinc. I can guarantee that no NCRS judge can tell the difference by looking at properly plated parts. I have plated parts for my own cars and many others, and have never taken one single point hit on any part I have ever plated.


Regards, John McGraw

 

John, I'm very impressed with your plating knowlege and ability to do it yourself. I've been using the Eastwood set for some years but not with the great results you achieve. I get a dull zinc. It does shine up with fine steel wool or other polishing but I wish I could cut out that step.

Nevertheless, the main purpose of my reply is to address the radio case plating. I think the thin sheet metal parts such as the gauge cans and radio case were tin plated. I don't have any document saying so but I believe it was tin. Your thoughts?

 

I stand corrected. I looked at the GM drawing for the 1957 tach and I see it calls for the housing can to be zinc plated. No cad choice.

Still not 100% sure about the radio case though. I've had a vintage car radio restorer tell me it was electro-tin.

 

Appreciate your posts here.

I am restoring a '61 and trying to figure out which hood parts are to be plated and with what type of plating. Also want to know if the bolts are to be plated as well. The male plates show signs of having a yellow plating so I assume that was cadmium. Do you know if the bolts were cadmium plated as well? The female locks do not show any signs of a yellow plating. Should they be and if so what type of plating, cadmium. What about the two bolts that hold the female latch in place. And lastly, was the hood support cadmium plated? I appreciate you help.

Lou

 

Hi Greg,

I've been looking though this thread for help with hood latches, hood support and bolt plating. I have a '61 that I am restoring for NCRS judging. What was your final decision on plating your hood latches (male and female), hood support and bolts?

Lou