After removing a wheel I noticed some deterioration of hub flange mating surface. I assume that it was originally a properly machined mating surface for guiding the wheel while lining up the lug-nut holes. Question: Does this deterioration of the flange indicate the presence of electrolysis between the more noble aluminum wheel and the less noble cast steel rotor hub? If this is the case, does anyone know of an insulating grease that should be applied to both parts? This seems to be a potentially serious problem.

Diardi