I grind the new welds, then soak just the weld area in Ospho, (phosphoric acid solution) second wet coat and then neutralize with water. BR CAREFUL, if not neutralized you can get a reaction with the epoxy primer you apply over it!!!
I treat inside of doors and any other area I an get to and used either epoxy primer, then then urethane or enamel topcoat, then undercoat etc. Inside of doors and insides of trunk extensions and inside of fenders at the brace are always waiting to bit your *** later!
