I just recieved on old gerry can for free and it is in relatively good shape. I noticed that the inside is a little scaly and i was wondering if anyone knew the name ofthe product that you can just put in the tank, swirl around and be done with. It is like a sealer. I am sure there is a step that loosens and cleans out the scale and then the sealer goes in. What the heck is tha name of the product. Anyone?