I have a 13 gallon tractor gas tank that developed rust in the tank from old gasoline. I had flushed the tank two years ago using some small stones and water shaking the tank the best I could. I installed the tank and used it for the two years when more of the rust broke loose and finally plugged the gas line. I removed the tank and this time I put small nuts and bolts with 2 gallons of water and strapped the tank to another tractor wheel, driving it for about one hour. The tank appears to be clean of any large pieces of rust but the walls of the tank and the baffles walls have rust on them. Reaching in with a scrapper I can scratch the rust off and the metal appears to be in good shape. What can I use to remove any more rust? I have read about muratic acid but am amprehensive about using it as more rust could develop. Do you have a product that will improve the condition of the tank.