the steel tanks the painter seals the bike tanks i do. i do not know what they use. i have done sumps with no sealer and alum tanks to with no sealer just do a psi check with some water in a spay bottle the sealer that they use on steel car tanks was por-15 and you could look at kbs to .i wash them out in the jet washer and have wash them out with dawn dish soap at the car wash i run about 3.00 bucks thru the car wash that works to i wash them till i can not smell any gas