Had a fire - repaint question

[BobPell]

The rear 1/4 had some fire damage and needs repainting plus some plastic parts replaced.
But what about the underside of the fender, I expect that it needs to be protected or will just rust thru. Am I right about that or can it be protected with an undercoat spray?

 

[Dream On]

If it were me, I'd sand it and paint it to be sure that it wouldn't rust, and then use the undercoating, as you said. But you may be able to get away with the undercoating.

 

[DSMGSX95]

Any time you have to replace body panels you should always repiant the inside of them prior to installation. In the case of fire damage repair, if the insdie of the metal surface was damaged by the fire then it needs to be 'treated' in some manor to prevent rust. If you can easily access it, sand, primer and paint the surface. If you can't get to the inside surface to do that you can you a chemical corrosion prohibitor that allows paint or under coating to be applied right over top.