Painting question
 

Here's the scenario, I will be cutting my car frame and adding a few inches of metal and then adding plates for reinforcement. My question is the what should the backside of the metal being welded be painted to prevent rust ? Is epoxy primer enough ? I know I need clean metal to weld to just concerned about what I can't paint after the welding. Thank for any input.

I've used the POR15 system on some things. Properly applied, that stuff does one heck of a job! And what I mean by properly applied, either applied to pourse metal (like something that was just sand blasted) or using their metal prep spray and it has a great bond to the metal.

I'm looking at nice shiny new metal not pourse. I'll check out that brand. Just hoping for something that will stick too and seal that side , I know some will be ruined from welding heat but anything is better than nothing.

As you mentioned, whatever is at the weld bead is going to get cooked off anyways. Maybe a weld through primer would hold up closer to the weld?

I haven't heard of this kind of paint before is there a brand you can recommend ?

The only kind I've ever tried is the Eastwood brand.

I'm not even entirely sure it would help though, but it does hold up well right next to welded areas.

POR15 can be used on smooth/shiny metal, but would require the metal prep. But it would have to be done after welding (properly applied, it is near impossible to remove.