Relative to a lot of other things on our cars, zinc or cadmium plating is a bargain. Part of that reason has to do with the fact that it is a batch process that doesn't require a lot of extra hand work like chromium which is all about the buffing and polishing. Zinc and cadmium are done in a barrel.
Cadmium is a bright bluish silver by nature, a bit brighter than zinc which is a a dull gray. Both get the yellow coloring in the same way--with a phosphate wash after the plating is done. That's a bit of a simplification but there's a lot of information available on the nature of the process on the internet. For those doubters who say "don't believe what you read on the internet" a lot of it is from technical journals, metallurgy magazines and related.
The yellow or gold color will vary greatly depending on a variety of factors. A former member here Bob Possel had a lot of cadmium plating done and wasn't satisified with some of the results; I've had good luck. The largest cost is in the initial batch. Each additional part is insignificant. That being said, it isn't like chrome where you pay by the part; what you want to do with zinc or cadmium is get a large batch all done at once.
The Cadmium will retain its appearance a lot longer than zinc. Contrary to some often repeated comments, there are plenty of places in the USA at least, that do cadmium plating. Just have to look. I've had it all done--zinc, cadmium, chrome...
Also there are some do it your self kits, and some members here have had great luck doing some yellow zinc by themselves. There's something to be said for being able to pull off a part on a Saturday morning, one part, plating it and having it ready shortly. However all this plating involves nasty chemicals, so pay attention to the safety instructions! Wallace Wheeler? Want to weigh in on the DIY side?
