Yellow Plating in MB

[Pawel66]

It is probably not very relevant, may only slightly contribute to overall knowledge base, but not a lot of effort to share or read.

My W463 300GE (M113 engine) is 1991 manufacturing (Graz) for Austrian market. Every bolt, every washer and nut, every bracket, every bracket being part of a bigger component, e.g. wiper motor, vacuum switch, etc., every pipe I unscrewed/undone or removed was yellow plated. I simply saw the remaints of yellow plating in hidden places on those parts.

I do not remember when was the environmental regulation introduced that marked the end of yellow plating, but I was pretty surprised, actually.

[wwheeler]

People get plating type and color confused all the time. So the type of plating and the color are two separate entities. What you are referring to in regards to regulation, is the restriction for CAD plating. CADmium plating is quite toxic and is used now only in very limited applications where its properties are required. Zinc plating has long since taken its place as the more available type of plating. Each has its own pros and cons. The appearance between CAD and zinc without color are similar. CAD is a little more dull, but both are silverish.

Now color has little to do with the type of plating. The color comes from a chromate which is applied AFTER the part is plated. The chromate's job is to further protect the plated surface which is vulnerable to attack from acid among others. So the colors can be yellow, clear (slightly blue), black and even olive drab.

My guess is that what you have Pawell, is yellow zinc, not yellow CAD.     

[Pawel66]

Wallace, thank you! It is obviously too technical for me, that is why I am writing "yellow".

 So I understand that, sort of, disappearance of the yellow colour on plated parts these days is not about CAD plating ban,  but something else (better methods, cost, etc.). This yellow colour was a result of certain chromate used and it was on zinc plated parts.

Pity... the  engine bays look much better with yellow plated details, I think.

[wwheeler]

Not sure why car mfgs chose the yellow color or the more common clear for the plated parts. There are also other finishes that are beyond my knowledge on modern cars.

Parts that I have had plated for my business were yellow for the simple reason it was easy to tell if it was plated or not. Clear chromate only has a very slight tint of blue and is difficult tell apart from a piece of clean metal.   

[Shvegel]

In my experience plating yellow hides more mistakes.  slight imperfections in the zinc will dissapear in Yellow bath.  Also the yellow uses chromium dioxide which might make it a bit more resistant to corrosion.