First off, maybe this should have gone in the Material Engineering thread, but since it is so common in the EE field....well, I justified it. I have an aluminum housing which gets plated with Ag over Ni. Once received, the housing goes through the following process: Cleaning (alcohol solution) 220 degree temp cycle for 2 hours. Send out for RF pins to be installed and leak tested. (Consists of heating, soldering, cleaning, leak testing with Helium) After the parts return from leak test, they have a brownish/redish film on the housing. Any suggestions as to what this might be? Bad plating? Bad raw material? Dirty cleaning solution? Any help would be great...thanks.