Ive used Enviro-Prime 2000 at the shop, only in areas that can be reached from the back side. When i can reach it, i dont use anything, i just coat the backside with POR-15.
i used the stuff from 3m, but i dont really get how it works, i sprayed a piece of metal and welded the back of it, and it just flaked away, but i coated my taillight fillers and that area of the bed before i welded it anyways.
3M's 5917. Good product, but like mentioned above, not really sure how it works. Guess it forms a chemical bond when welded that allows the other stuff to flake off.
Chris
well what ive been doing and im not sure how well it works but anyways....i use the iron oxide primer and lay it on really heavy on the backside of filler plates and shit. I know its gonna burn off somewhat but hopefully it works well enough. I didnt know if there was a better thing to use or not.
the 3m stuff is good if you can get more than 2 sprays out of a can..for some reason they NEVER work...BUT i found that NAPA sells a much BIGGER can than 3ms..its also cheaper and u can spray the whole thing til empty unlike the 3m..and it appears to be the exact same shit
i agree with trevor about the 3m stuff clogging ,not only that it cost about 3 times what other comparable products costs my shop is using wurth weld thru now