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

 

Any time you have two dissimilar metals in direct contact you will have electrolytic corrosion to some extent. The question is how bad is it? My guess is the "deterioration" you see on the mounting flange is actually coming from the wheel and most of the time this is just surface discoloration and is nothing to worry about.

Examine the wheel and flange for any signs of pitting or cracking. If you don't see any then you have nothing to worry about. If the discoloration bothers you, you can remove it with a stiff-bristle non-metallic brush.

 

Thanks for the input. After I wrote my original, I contacted an engineering friend who corrected me: Aluminum is less noble than cast iron and the aluminum surfaces are in good shape. I'm scheduled to go over the pitting on the cast iron with the local Chrysler dealer, so I guess what I found is probably pretty normal.
Thanks again for your input.
Diardi 2004 Blaze Red Cpe. 13,540 otherwise happy miles.