After you clean to bare metal where the ground contacts are made, that bare metal will soon rust and corrode. Some people suggest using non-conductive dielectric grease to minimize the corrosion; however, a conductive anti-corrosive grease is far superior at grounding points.

"Kopr Shield Colloidal Surface Treatment
Kopr-Shield compound is a unique homogenized blend of pure, polished colloidal copper, rust and corrosion inhibitors that simultaneously protects, lubricates and enhances the conductivity of the mating surfaces to which it is applied. Extremely adhesive, Kopr Shield compound flows smoothly into uneven contours and voids, making application easy, protection and lubrication complete and positive. A stable compound, it will not settle-out, thin, thicken, harden or dry out under the most severe environmental conditions."


Eastwoods and many electrical-contractor supply-houses sell this product.