I recently pulled and old ugly motor out of the barn to put in my bike after messing up the original one. It was corroded, greasy, just plain ugly. I brushed on muratic acid and let it sit a while, cleaned off the corrosion nicely. Muratic acid is not the best to use, but I had it lying around. I would have preferred to use phosphoric acid, it doesn't discolor the aluminum like muratic does. Acids will take the plating off the screw heads and such, but will not hurt chrome.