Need Opinions on rust damage - Fix vs Replace

[ZombieK5]

Warm weather in Philly is in full force. I am working again on the two donor rear quarter panels I got last year. The passenger side has some corrosion/pitted areas near the gas tank fill door and the back lower edge below the taillight.

The corrosion does not go thru the panel and I could media blast it to get down to fresh bare metal.

Options:

1. Cut and replace pitted area with metal from purchased panels or other donor panels.

2. Media blast metal down to fresh bare metal and use good body filler.

Body filler method would be less work, new panels would me a solid solution but would take much more time.

Thoughts or ideas?

(Please excuse the surface rust)

 

[bp71k5]

High build primer would probably clean most of that up after sanding the rust off. Looks like a few holes rusted through.

 

[Jimmy85]

I think I hear an old timer saying he would spread some lead across there! just kidding
If you're going with the body putty to fill the low spots, I would agree to media blast said areas first. Then if the panels felt thin, maybe some fiberglass behind the panel to give strength.
But I don't think it's bad enough to merit stitching a new piece in there.

 

[ZombieK5]

I think I hear an old timer saying he would spread some lead across there! just kidding
If you're going with the body putty to fill the low spots, I would agree to media blast said areas first. Then if the panels felt thin, maybe some fiberglass behind the panel to give strength.
But I don't think it's bad enough to merit stitching a new piece in there.

You actually read my mind. I was going to slap a few layers of cloth Mat with poly resin behind the bad areas. It will add some strength and thickness. Eastwood has a really nice polyester body filler. Thinking that will be the route I am going to take.

 

[Clark75K5]

Test some of the worst stuff with some sort of pick type tool, if it doesn't go through I'd use it. Definitely use some sort of filler for the pits, I really like USC 26006 for lighter repairs like that. Setup time is about perfect and it smooths out great. Remove all the rust first, and I'd epoxy prime over that area as well.

 

[ZombieK5]

Test some of the worst stuff with some sort of pick type tool, if it doesn't go through I'd use it. Definitely use some sort of filler for the pits, I really like USC 26006 for lighter repairs like that. Setup time is about perfect and it smooths out great. Remove all the rust first, and I'd epoxy prime over that area as well.

Epoxy prime, body filler and ready to go? Still plan to use fiberglass Mat inside behind the pitted damage.

 

[Clark75K5]

Yes, once the panel is all cleaned up. You can do it in either order, but filler actually sticks to bare metal better than it sticks to EP. But for it to come off you'd have to wreck your truck pretty bad and you have bigger issues to worry about at that point!
EP is fantastic stuff.
Beware of sandblasting panels in large flat areas, the etching process makes it so the outer panel has a greater surface area than the inner, and this causes oil canning. Remove as much as you can mechanically, blasting shouldn't hurt the areas closest to the stamped edges.
(I of course learned the hard way - trunklid and hood on my GTO needed a lot of work with a shrinking disc)

 

[ZombieK5]

Yes, once the panel is all cleaned up. You can do it in either order, but filler actually sticks to bare metal better than it sticks to EP. But for it to come off you'd have to wreck your truck pretty bad and you have bigger issues to worry about at that point!
EP is fantastic stuff.
Beware of sandblasting panels in large flat areas, the etching process makes it so the outer panel has a greater surface area than the inner, and this causes oil canning. Remove as much as you can mechanically, blasting shouldn't hurt the areas closest to the stamped edges.
(I of course learned the hard way - trunklid and hood on my GTO needed a lot of work with a shrinking disc)

Gonna ask for very fine media for exterior surfaces. I think I'll mechanically remove the majority of paint on exterior surfaces and have them blast the pitted area to get bare metal. Media blast on all the corroded surfaces then POR15 the unseen parts.

 

[Clark75K5]

Solid plan. No reason you can't EP the inside too unless you just aren't going to strip it. EP is also suited for applying over original coatings such as old lacquer paint.

There are other medias (black beauty, walnut shells, plastic media) that will remove the rust and not harm the metal. On those types you'll need to scuff up the surfaces prior to EP. Sandblasting leaves an excellent tooth for EP so nothing is needed prior to spraying other than a good wipe with wax & grease remover.

 

[ZombieK5]

Solid plan. No reason you can't EP the inside too unless you just aren't going to strip it. EP is also suited for applying over original coatings such as old lacquer paint.

There are other medias (black beauty, walnut shells, plastic media) that will remove the rust and not harm the metal. On those types you'll need to scuff up the surfaces prior to EP. Sandblasting leaves an excellent tooth for EP so nothing is needed prior to spraying other than a good wipe with wax & grease remover.

I'll post pics and updates on my build page. Should be starting soon. Just trying to figure out the science of removing the old qtr panels and weld/bolt replacements in place. I'm having the new tailgate support beam zinc coated and black powder coated. It goes in first then the qtr panels go in. Gonna be fun

 

[Blue85]

POR15 the unseen parts.

Bad plan. Stick to the EP that's been recommended here. POR15 is no epoxy and is not intended for spot repairs. It will peel off later. Plus it's too thick and a pain to sand. You may be avoiding the spray gun, but then how are you going to paint it? I think you can get some 2-part EP in a special rattle can now if that's the concern.

 

[ZombieK5]

Bad plan. Stick to the EP that's been recommended here. POR15 is no epoxy and is not intended for spot repairs. It will peel off later. Plus it's too thick and a pain to sand. You may be avoiding the spray gun, but then how are you going to paint it? I think you can get some 2-part EP in a special rattle can now if that's the concern.

I understand the "bad plan" and you'd be right however I have been talking about replacing BOTH of my quarter panels. The donor quarter panels are in bad shape in several parts. The POR15 is primarily for the inside sections of the replacement B Pillars. EP will be used for the pitted steel over the body filler. The Por15 will be used by itself along some inside body panels along with some fiberglass matting. I attached two images from one of the two donor quarter panels. The other is actually worse and has more corrosion inside the B pillar. I have Epoxy Primer for the entire outside of the quarter panels as wells as most of the interior.

 

[bp71k5]

I’d stay away from the POR15 as well.