Some people claim that after cleaning the engine and leaving a thin film of a light oil, like WD-40, helps slow this effect. I cannot say for sure how well it works. You DON"T want to scour the engine with a steel scrub pad as it will leave minute bits of steel, which will promptly rust. Those non-metallic scouring pads work pretty well.
You could also possibly use a soda-blaster (bicarbonate) to clean up oxidized parts, though this does nothing to prevent oxidation from coming back. The soda leaves a film of bicarbonate which will attract moisture, so it may be a good idea (ESPECIALLY if planning to paint something that's been soda-blasted) that you neutralize the soda by washing the thing down witha mixture of vindegar and warm water.