That black primer or whatever it is that new panels come in, do you sand that off or can you weld thought it? prime over it? probally a dumb question but not sure what it is...thanks for help graemlins/thumbsup.gif

Give it a light Grind, and use a weld-through primer to prevent corrosion. You can get weld through primer in rattle cans from your local auto paint supplier.

Shouldn't you spray the back side of both pieces of metal with primer, then weld, then spray the front side with primer (just regular primer)? If you lap weld I can see the benefit of weld through primer, but for a butt weld is it necessary?

with a butt weld there should be no weldable primer or anything applied to the weld area. Keep the metal clean and make some nice welds then clean and coat the backside with a good metal etch or epoxy primer and paint, or finish then off inside in the visable areas with duraglass or everglass then primer and paint. The nice thing about a butt weld it there are no areas that can't be treated, no airgaps between two panels for corrosion to start. Take apart any pinch weld or lap joint and you'll usually find corrosion, heck years ago I replaced a doorskin on a new car that was lot damaged and the bottom seam on the door had rust already and the car was new! Bottom line is if oxygen can get to bare metal it is going to rust.

To answer the question (I thought I was the guy who always got sidet racked smile.gif ) that black primer is "E" coat and zinc rich, it does NOT have to be removed. It is basically a super high quality weld thru primer. That is IF it is real "E" coat. Take a thinner soaked rag and try to rub it off, if it holds up it is probably E coat.

Sorry, sometimes I do get sidetracked :D

thanks guys for the help ya'll are the best graemlins/thumbsup.gif it's getting welded on tonight.