it's highly recommended that the tank be coated inside if it's been rusted - otherwise the bare surface left inside will continue to corrode, and regardless of the 'bits' that might plug things up [or get stopped by a filter], eventually you'll be faced w/ pinhole leaks showing up, especially along any seams
as Tiny sez, the internal corrosion will occur most at the level that is at the surface of the gas level due to the temp differential of gas and air causing condensation there, and a properly applied coating will not cause later problems, but prevent them
once rusted, the tank is on it's way out if it's not coated - "just keep the tank full" would hafta be fill it to overflowing and never drive it, and gas does evaporate!!
Bill
