Given the stain line on that pump, Terry, do you think the rust accumulation was more from storing the tank half full of gas for prolonged periods or from the use of ethanol fuel? I know ethanol gets a bad rap by lots, and I'm one of them, but I'm also of the opinion that half-full storage even with pure gas will create rust.
It's always been my practice to store full or empty to avoid such a problem. With no room (full) for expansion and separation, the rust is prevented. With no fuel (empty) left, there's nothing to separate and create moisture.