There is a paste available at electrical
supply houses that you must use for using aluminum
high voltage wiring
, it is there I believe to prevent oxidation of the wire, not too many years ago houses were burning down that had aluminum wiring
, the wire would oxidize, heat up and the heat expansion and contraction would loosen the connection which of course caused fires.
I'd clean up the faying surfaces and use this paste, it's cheap
, and or maybe install a case ground on the starter itself
I think the only thing that will remove aluminum oxide is physical force, scraping or maybe sanding