Quote Originally Posted by Canoehead View Post
(and can be worse when next to steel - something about dissimilar metals and galvanic something . . .)
Very true. When we do brake jobs on Semi-tucks and trailers, we put a feltish-teflonish or thin-plastic gasket between the aluminum rim/wheel and iron brake drum. The chemical reaction between the two if they are in contact is impressive. I have seen aluminum rims corrode and structurally fail because of this reaction. We use the same type of gaskets when replacing steel cross members on trailer floors that may contact aluminium floor or side rails.