Can we Passivate Cadmium Plating?

A. Hi Mike. I don't think there is such a spec as AMS 967; your customer probably meant ASTM A967, but my guess is that he is confused and needs your enlightenment! I would be very surprised if anyone truly wanted their chromate conversion coated, cadmium plated, stainless steel to receive a passivation treatment designed for bare stainless steel, and I think it may all just be a semantics confusion: while stainless steel is "passivated" with nitric or citric acid , the chromate conversion coating operation on cadmium plated parts is sometimes called "passivation".

I'll bet the customer wanted to indicate a spec number for the chromate conversion/passivation on the cad plating and got confused. Good luck sorting this one out :-)

Regards,

A. Hi Mike,

Cadmium plating Passivation is entirely different compared with Stainless steel passivation.

ASTM A967 describes Corrosion resistant stainless steel passivation, which is not linked with any (Cadmium) plating, and it is a process done by Nitric acid or Sodium dichromate or both.

But cadmium plating passivation or chromate conversion coatings are of three types 1.Blue or clear, 2.Yellow, and 3.Olive Drab. These passivations can be either trivalent or hexavalent.

These three passivations are done after cadmium plating as a post treatment of it.

Regards,

A. Hi Jacky. You also seem to be speaking of chromate conversion coating "passivation" of plating not the passivation of stainless steel. Yes, I think you should make that change now that ASTM B633 offers it. Personally though, if something needs to be RoHS-complaint, I would still include the phrase "RoHS-compliant". Sometimes the plating shop, or someone else along the line, may know more than we do about what is and isn't compliant, so I wouldn't take the shortcut of leaving it out. For example some brasses are not compliant; and in the past if not present, some electroless nickel platings were not RoHS compatible.

Regards,