Blueing (blackening) of stainless steel
How (with what) can you tarnish (blacken) stainless steel?
Insanely tight. Almost impossible. Well, as an option - all sorts of black chrome coatings and spraying. dye.
If you're talking about the bushing, the paint will rub off. Maybe you can try it with electrolyte, as HP-2000 advised.
I don’t know, I tried blackening stainless steel with “Super Blue” and “Ekhkalibr” - it always worked. Not the first time, but ink.
Absolutely right