I'm welding in new steel into my tub where the red cancer has got her. I'm a little worried about the places where the metal has to overlap a little 'cause this seems to be where the old tub rusted out first. I remember hearing about this primer that you could weld through, made of zinc or somthing. Does anyone know what I'm talking about? If so, how well does it work? Where can I get? I figure if I put that stuff in there, seal up the seams good and It might last even longer than the original tub. What do you recomend for sealing the seams by the way?