[AcampoDave]

As a pool service guy I just gotta warn you guys that muriatic acid is pretty caustic stuff. It fumes heavily in humid conditions and can be leathal when mixed with certain chemicals. (Like chlorinated compounds.) It does remove rust but will also eat clean metal too if given time. If you go this route I would not seal off the reaction in any way that could trap pressurized gasses in the tank. And be smart wear goggles, and keep a water hose within reach. Don't mean to be a mother hen here, but I use this stuff every day and its powerful stuff. It's safe in a pool but....you know what I'm sayin' here right?