I have seen the postings for using batteries for etching. The
methods describe using copper. Does anyone know if this will work
on brass, bronze or nickle?
It will work well on any of those non-precious metals. You will need
a different solution for working in sterling or gold, but the salt
water is okay for the base metals. There is actually an article in
Art Jewelry Magazine this month about using batteries for etching
base metals. You might want to check it out.