Saw this on Youtube and tried it out myself.

Apparently, you can make nuts and bolts as well as relatively small pieces of metal rust-proof by fusing carbon on it. It's better than paint as it won't chip off once cured.

Of course, I had to try it out. I gathered a bunch of rusty and pitted bolts.



I gave it an acid bath to remove most of the surface rust.


After several minutes, I washed them off with a baking soda solution (to neutralize the acid) then rinsed with tap water.


They look very clean now but at this state, rust will quickly form (flash rust) if you don't put any coat on it.


Next up is torching them until they're red hot.