Something to do with electricity & chemicals lol I didn't work on the line. So I don't know much about it. I just masked off certain areas of parts either gun, aircraft or medical to ready for the process or did quality inspection & packing of parts
As far as my understanding Basically, any metal that isn't naturally colored but needs to be has to be plated to go into the next process of anodizing..
Like the black coat over guns.. it has to go through that process of plating before the coating (anodizing)
Electroplating - Wikipedia, the free encyclopedia