fixing various rust spots. What to coat inside with?

[adam78280z]

I was going to buy a new 4x8 sheet of 18 gauge mild steel to use for some of my repairs. BUT instead I decided that since i have a couple parts vehicles at my parents house i'm just going to cut what I need off a hood from a Jeep cherokee

 

I have a full RustSeal kit for when I finish the engine bay and floors, but what should i spray on the backside of the patch pieces on the rest of the body. Would a weldable primer work to prevent rust on the new panels in the future? I just want to do this rust repair once, not again in a year!

 

Thanks,

Adam

[WizardBlack]

Primer will not prevent rust over long periods of time. Etch the metal and then use POR15 or Rust Bullet, etc. Don't forget the etching portion or the stuff won't stick as well as it could.

[adam78280z]

Primer will not prevent rust over long periods of time. Etch the metal and then use POR15 or Rust Bullet, etc. Don't forget the etching portion or the stuff won't stick as well as it could.

 

Will the rustseal/por15 hold up to the heat from welding? I was afraid that I would just be wasting material if I pre-painted it, then welded it. I'll give it a go and see what happens.

[Scott_M67]

No, you need to use a weld through primer in your weld areas then POR or epoxy prime everything else to prevent future rust issues. Don't forget the seam sealer too.