5 replies to this topic

[neon1991]

so ive been having a bit of a back and forth discussion with an online parts supplier who advertised yellow zinc brake parts but actually supplied the standard silver zinc coating. It used to be the case that yellow zinc had better rust protection than the silver.  the parts have been on the car a week and already showing signs of red rust (not ideal on brake fittings.  can anyone confirm there is a difference?

Edited by neon1991, 28 August 2018 - 04:22 PM.

[DeadSquare]

Good, thick, so called "Yellow Zinc" was very good, it had chrome and cadmium in it, but I haven't seen it for about 20 years.

 

People still talk about yellow zinc, but although zinc sometimes has a slightly yellow tinge, "It ain't what it used to be".

 

If rust is bleeding through after a week, the surface of the item either wasn't prepared correctly or far too little zinc has been deposited.

[Spider]

I have a lot of parts re-plated on a regular basis. I was having straight 'Zinc' done but found to 'chalked up' within about a year or so. I swapped over to 'Yellow' (as they call it) which they still do the same Zinc Plating and then do the 'Yellow' (or 'Gold') over that and I'm finding it is WAY better, still looks good several years later.

 

I think as deadsquare mentioned, it used to be Cadmium, but I'm sure that's gone from it now. What ever it is, I find it good.

[A-Cell]

The additional coating after zinc plating is called passivation. This improves the corrosion resistance of the zinc plating and also adds a colour. The yellow is achieved by using Zinc chromate not cadmium. None passivated zinc electroplating goes dull and gets a white oxidation on it.
The zinc coat acts as a sacrificial anode protecting the steel underneath.

[neon1991]

I knew I wasnt going mad.  this parts supplier said "it was news to them".  I'm not a parts manufacturer and I had an idea that there was a difference,  surely the parts company sending batches for plating should know what they are paying for.... apparently not.

[Curley]

Na, part supplier probably knows less about the parts than you do, 99% of them just want to sell you stuff & if it's a duff then they can sell you two.