Like it has been on an extended deployment in space. Look closely at a US Navy surface warship that has been on an extended patrol and you will see plenty of rust stains and discoloration.
I was on one of those forward deployed (the Med, homeport Naples) U.S. warships (a DE, looking for Russian subs) for two years. Toward the end of that time, the ship had collected more than its share of rust stains, but we could literally run circles around the freshly painted Russian cruisers that attempted to shoulder us out of the way.
Especially since they lost Mary Sou's side cleaners, at least in the Pacific.