Distinguished SOTW Member, Forum Contributor 2014
I had a hunch that of course acid would remove the corrosion. I used a 1/3 HCl solution and put the keys in there for about 10 minutes and shazam, the tarnish was gone, but I forgot one thing, That German silver has a significant copper content, and so the keys developed a slightly coppery tint, which actually doesn't look bad. Then just hand polishing to make them cute. The corrosion was atrocious, and would have taken days by only hand polishing. I forgot, I remover all of the springs prior to dropping the keys in the solution. Anyway just something that I tried that worked extremely well and quickly. Hopefully some of the hardcore guys will post something as well.