It does some weird stuff .Like deteriorate from the inside out .Like for example an aluminum storm door in contact with concrete the outside looks fine but the inside has rotted like it has metal termites . The inside portion of my avatar saw ,the cover of the oil tank of all things had damage inside . Aluminum ,mag ,zinc are known as sacrificing metals .They go to the dogs before other metals do thus in a way protecting them . The plating that cover certain pistons is on there for two reasons .First the plating grabs oil better than bare aluminum plus it protects from galvanic reaction between dissimilar metals .Now as with a lot of babbling I know more than most people about metallurgy but I'm dang sure not an expert .