rust..... have had my share over the years, I've come to agree that the only real way to stop it is to cut it out where possible, otherwise I take a grider to suface rust and bring it back to shiny metal then seal it and fill and finish. have tried the por 15 and rust converters but they all seem to be second best and buy a little time. on surface areas that show I try to use the shiny metal routine. cheers, mark