It doesn't really matter if it has corrosion on it....thats just the very outermost layer of the metal....on the newer motors its under a plastic cover anyways, probably why they did not treat the metal as much.

I imaging you could remove it, sandblast or abrasive brush it, polish it, then clear coat or paint it with a temp resistant paint and then it would stay looking good. The old ones on the M103 M104 etc were just painted black.

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