I've seldom seen anything come out of a "hot tank" that did not have residue on it, and had to be scrubbed with a brush or pads and soapy water. All the tank does is take away all of the loose dirt and loosen the crusty stuff so's it can be scrubbed off. After you wash it and have it nice and clean and shiny like new, lightly oil the inside, and the pan rail, and get some paint on the outside pretty quick so it wont flash rust on you.