Best way to remove rust from black oxide?

Sorry, I should have said it doesn't hurt good paint. Old paint is another matter, as it took the paint of a a 1937-ish AA hobby lathe. As for bluing, since it's basically a form or rust, it makes sense that it would remove that. So in this case it might not be what the OP needs.

Does electrolysis remove bluing?

Rex

That OP would be me. I was pretty excited (and amazed) when you first stated that EvapoRust wouldn't hurt finishes (the implication being that it wouldn't hurt black oxide, since that was the subject of this thread); I thought perhaps that the chelating reaction was limited only to pure rust. Oh well...

So now I'm wondering what makes EvapoRust so much better than a bath of vinegar and salt (besides perhaps the speed of de-rusting)?

Btw, can anyone tell me what is chemically different between rust and black oxide. I know that black oxide is a more durable oxidation film than rust, but what makes it adhere to the surface of the steel better? And what makes it black/blue?

- Michael

One is Fe3O2, and the other is Fe2O3 I believe. I can never remember which is which. The red stuff is both porous, and expands as it forms, which is why it continues rusting & eats holes in things. The black version is non-porous, and seals the metal underneath, sort of like anodizing on aluminum does. One thing I hadn't realized until a few years ago is that one way to make the balck version is to boil the red version. They sell blueing chemicals that form a thin layer of red rust, and when you boil it, it turns black. Because the original rust doesn't cover theings completely, you need to repeat this a few times to get a really good coat of the black oxide, but it works very nicely on smallish parts.

Doug White

replying to DeepDiver, MarkTop wrote: How about using ospho .?