Stripping 316SS after accidentally zinc plating it

A. Paul: Here is a reply to your question by Max Stein, who has been doing alkaline zinc plating for many years:

"Zinc oxide: Alkaline zinc plating solutions are famous for co-depositing a matrix of Zinc oxide within the metallic Zinc. Most probably, that is what it is. Right, it must normally be white, but when talking about very small particles … (As plated, coating from alkaline zinc are often yellowish to brownish-green: due to the same phenomena). It is not easily dissolved neither in hydrochloric nor nitric acid. Reprocessing through alkaline clean - hydrochloric acid - scale conditioner (hot caustic with potassium permanganate [on eBay or Amazon]: often used in passivation pre-cycle on heat treated CRES) will definitely help.

Another option - concentrated chromic/nitric acid mix. It must be interesting to see if you have obtained a reasonable degree of adhesion: bend or file test can be done. If adhesion is very good (which I doubt very much), you may have developed a new method of activating CRES. Cheers, Max"

A. Sometimes SST will plate just fine without a nickel strike. I never could figure out why. As for the smut after stripping zinc, try soaking for 3 minutes in a spent (or new) cyanide based nickel stripper (room temp).

A. Paul, you are really putting your plow into new ground, I have never heard of anything like this before, and I am fascinated. I would like to take a look at the problem, and do some research work to try to determine what is going on, and how to resolve the issue. If you send me parts, I will do the work, and report to you on what results we got.