The archives contains an item by David Huffman on rust removal. It
is a very simple approach to cleaning up some neglected tools which
have become rusty. The process involves a sort of reverse plating
that turns rust into a black powder coating.
My question now is: What exactly is the black coating and how can it
be removed? Some can be wire brushed off, but not all. I tried a
quick dip in nitric acid which removed some, but it is a pretty
drastic approach. It would be nice to end up with bright metal and
no residue. Any suggestions?