Rust pitting repair

[JoshStratton]

I took my fender off to repair the rust bubbling. Fortunately it isn't as bad as I originally thought. I sanded it down to bare metal, and now I have 5 or 6 small spots and one HUGE spot that are not rusted through but they have left some pitting and there is still some rust that I cannot sand out of the little holes. This brings a few questions:

1. How can I remove the rust from the pits.
2. How can I fix it so the rust doesn't come back...should i just use some putty and treat it as a normal primer and paint?
...how would a professional body shop tackle this?

As you can probably tell...I am new to this.

I really don't want to sand the pits down flush and build it back up with putty. I would rather leave as much original metal in tact as I can. I guess I could go with the option of cutting it all out and fabing a piece to match...but I think it would be pointless since there is so much good metal left.

[Happyfunballs]

You have a few options:
-Spot sandblast the pitted area.
-Grind it off and fill it
-Cut it out and weld in new

Whatever you do, eliminate the rust.

A professional bodyshop, in the interest of time and money and depending on the severity, would grind it out and fill it.

[Jim Nilsen]

POR 15 when done properly will stop the pits from bothering you for many years. Do both sides to be certain and follow the directions exactly. POR putty or simple a/b epoxy will fill the pits with no problem.

If you have the skills to patch it with new metal you will have a btter fitting fender than if you buy a repro and it might cost less in the end even if you paid a pro to fix it.


Jim Nilsen

[JoshStratton]

I started grinding it down and I am afraid it may be too much. If I keep going I may pop through in a few spots. I know I will have to patch one part of it, but I would prefer to limit the amount of patches I need to put in.

I thought about the POR15. I was going to use it for the pan and anywhere the sun don't shine, but I was not sure of the outside of the car. I have never used it under putty or paint. What are the possible threats to my fender by doing it that way?

...I just looked at their site. Were you talking about the PorPatch or using the STRAIGHTLINE and RestoGrip solution? That might actually be a usable solution.

[Milow68]

I would not use POR15 under any kinda putty!!!
Some of the pits could be welded over (the little pits, one quick shot with the Mig, not a steady bead).
Cutting out and patch is a very good way to deal with it.
Definately sand blast!! or you will see the rust again.

Just the old .02
Brad

[JoshStratton]

POR supposedly has a putty system that is formulated to be used over the POR15. It is supposed to be pretty good....hmmmmm

I almost want to try it just to see what happens.

[JoshStratton]

I told my wife I might be making a trip to the body shop and she suggested something I had not thought of. Since I grounded the bulk of it down, she suggested using the dremmel to clean/scrape out the holes that still exist, and then fill them in. Anyone done this one? How did it work out?

[JoshStratton]

I figured I would give you all an update. I decided I would be a 'guinea pig' for the StraightLine POR15 product....after all, with every new product, someone has to be the first to try it. I will just get a new panel if this doesn't work.

So far, this is what I have done:
-Cut out part of the rusted panel and welded in a new piece
-Grind off all paint/rust
-Use Dremmel with grinding cone to 'dig' rust out of small pits
-Clean with MarineClean
-Apply MetalReady non-stop for 45 minutes
-Clean metal with water
-Apply POR15 as directed
-Wait 24 hours, sand POR15 and apply some more
-Wait 24 hours and scuff POR15 up with 300 grit sand paper
-Apply the StraightLine filler as directed and sand smooth
***This is where I am currently. I have my (hopefully) last coat (on my 3rd) of StraighLine currently drying. Tomorrow I will sand it and see how we are doing. So far, it sands very well and adheres very well...so far. We will see what happens when I spray the primer down. If it peels off of the car we can consider it a failure.

I am not that experienced with fillers, but I hear you are most likely to see your failures during the priming process. POR15 says that the StraightLine is 100% guaranteed and is the "best filler you will ever use" and it is supposedly formulated for going over POR15, so we will see how that goes.

[Happyfunballs]

Sounds good. Thanks for keeping us in the loop. It doesn't sound like you'll have any rust issues.

[JoshStratton]

1. I had a big rust hole in a fender and decided to patch it with new metal.
2. After doing that, I was still a little nervous about some pitting that I had around the area so I cleaned the holes out with a dremmel grinding cone.
3. Next I applied MetalReady and POR 15 over the entire rusted out area as the directions described. (I also coated the underside of the fender with POR15)
4. I noticed that the fender wasn't quite in the shape that it should have been, so I used some of the StraighLine body filler that POR15 offers. They said it should be put over POR15 that is a few hours old...follow the directions on this.

The stuff sanded VERY smooth and seems to be rock hard after a week of curing time (i dont think it takes that long, just had other stuff to do). I am not experienced at all with body fillers. This was my first time using them to this extent. I am VERY VERY pleased with the way it has turned out so far. It is kind of expensive, but I think the price difference was justified.

Unfortunately I did not document the process because I wasn't sure how it would turn out...but the good news(i suppose) is that there is more than one fender on that car that needs work
Now that I know what I am doing, I will document the next one. I hope to have it ready in a week or so, but we will see...

I primed the fender with RIGHT STUFF(very cool stuff and cheap too) de-ruster after sanding it to bare metal. I then sprayed it with DP40. The StraightLine part of the fender came out the best (by far). It's so smooth and it looks really good under the black DP40. No cracks so far and it has been about 2 days. I am told that with fillers, your biggest obstical is the first hour or so that you spray primer. If it doesn't crack by then, you are probably ok. I put the fender back on and it looks so much better...now if I can just figure out how to re-align the darn thing correctly.

[third base]

O.K., i know a lot of pople think that POR is the greatest thing ever invented to stop rust but that is simply not true. after applying POR it dries very hard and can eventually peel if done on edges. in order to use any kind of their putty(any kind!) the POR has to be tacky when putty is applied. then if you want to primer over it you have to break the surface quite a bit. don't bother using a tie coat primer for it is practically the same as a good epoxy primer just apply after POR has dried and use a few dust coats before you cover surface completly. I have had many discussions with the dealers in Sac, cali.. about their products. sadly i have found out the hard way and have personally used A LOT of POR. I don't even want to go into that. so if you have something to patch. cut it out, patch it, clean it, primer and topcoat. if done correctly you shouldn't have any problem with rust.
P.S. if you do use POR make sure to wear the proper mask. water is it's catalyst and it can dry in your lungs. it happened to me and I got very sick and all that happened was I could slightly smell it though my mask. Good luck!