So I picked up an '87 4Runner in January. I spent a lot of time looking for a low-rust truck, and I did pretty well, but there are a couple of patches in the usual wheel well trouble spots. Yesterday, I pulled the trim and went after the worst spot with the wire brush & sander. What I found is that it's pitted, but not rusted through except for two little spots smaller than the diameter of a pencil. (I found those spots by pushing on the metal with my Leatherman. It's solid around them, honest.) I expect the other spots will be in similar shape.

Worse than I'd hoped, better than I feared....

What now? This seems like nowhere near enough rust to warrant any welding, but how do I stop it here? Most of the rust repair threads I've looked at have been for much(!) more dire situations than this, but I'm trying to be proactive.

Here's a photo of the spot in question:

 

por-15 rust paint

 

x2,seal,paint!!!!

 

I'd sand that down some more and paint some POR-15 over it to be really safe, or just sand it down and hit it with some rustoleum if you don't want to spend the money on POR-15.

 

Well rust is caused by oxygen and water reacting with the iron so take those 2 out of the equation and your rust is stopped. So anything that will stop water or oxygen from hitting the steel and you will be fine.

 

I would sandblast the area, and re paint.

 

You need to get down to bare metal. I Would do the entire back half if you have the time, which isn't that much. Then you have to deal with the pits, so get a good fiberglass filler. Build up and sand until you have a smooth surface again.

At this point I want something that WILL NOT allow the rust to come back. So I use a good Epoxy Primer...PPG DP-90 (Part A) and the Dp402 (part B). Once that is set-up for about 2 hours I would go over with your top coat.

That's it...it really is that simple. A good epoxy primer over bare metal, the only way to go these days.

 

not trying to be that guy, but once rust is on your truck...its there forever. No matter what you put on top of it, it will still be there and eventually come back. Gauranteed. Have you cleaned off the back side of that panel? Because if you have holes right through the metal, its probally going to be just as rusty on the other side. So in that regard, if you don't clean the other side...your wasting your time. The only way to get rid if it, is to cut all the rust out + 2-3 inches on each side and weld in a replacement panel. And even then it will probally come back. (think of rust like mold on cheese, you can cut off the bad spots, but its just a matter of time) Putting fiberglass filler on top of what you have done will make it look good for a while. But eventually the rusting will cause it to lift and fall off. The filler should be applied over bare metal for proper adhesion (at least all the fiberfills I've use needed it). You'll need to cover the holes from the back side as well, as they'll let moisture in and speed up the re-rusting process.

 

Wow, thanks, guys, for the tips. @nothingbetter, I've heard that about the rust coming back and that's kind of why I was asking. But I don't really see room in the budget yet for welding new metal in.... I guess I'll work on getting down to bare metal, front & back, and try filler & POR-15 for now. I am in Colorado, things rust much more slowly out here than most places, so I've got that going for me.

The truck needs a complete paint job, really, I just don't want it to rust out while I'm saving up to do it right.