Calg5
Active member
I am new to this forum and if my question has been previously discussed, I apologize in advance. I have several PCB extracted from hight grade military equipment that are clad on top with a dull grey metal (probably oxidized). The metal is about 1/32" thick and is very soft. I am able to scrore it with my fingernail and expose a bright silver mirror like finish metal inside. I placed a drop of nitric acid on it and the metal remained passive for approximately and hour but then the acid penetrated through it. The acid remained colorless however. The cladding is non reactive with HCL or sulphuric acid. Is the metal lead and why would boards be clad like that. Your comments will be appreciated.
