The tank is looking great so far! That stuff takes a bit longer to work, but it doesn't eat existing metal like the acid cleaners do, and it leaves a film that prevents flash rusting. Not to mention that when it's done with your tank, it can be used to clean up countless rusty bolts, body parts, rusty chrome, and myriad other stuff. I'm still using the two gallons that cleaned my disgusting wrinkle tank.