For corrosion/pitting on the bolt body, scrub it with something like 4 ought 0000 steel wool and Hoppe's #9 solvent.
I suspect you are talking about pitting from oxidation (rusting) and not corrosion, per se'.
If corrosion, from acid, neutralizing the acid first with baking soda and water would be a good first step, then due to do the scrub.