[KMC]

Hi. My advice is to on no account paint the tank. Far from protecting, it can encourage corrosion. As long as the tank remains away from standing water in a ventilated area the bare aluminum is the best protection. With regards to the anti-syphon valve I am unsure if it is an ABYC rule for diesels but it would certainly make sense as syphoning a tank full of diesel into the bilge only to have the bilge pump throw it overboard could prove very expensive in fines should it be noticed. My advice is to leave it.