Hey guys, I know this is grey area as Im not doing it "proper" but I dont have the funds yet to do the car proper and strip the car fully.

Everytime Ive ever done body work within a few months it seems to look like crap and the rust bubbles so fast through. This last time I had a quarter sized rust hole thru on the rear quarters, I removed all the rust, was down to bare metal in the section, then I used Rage body filler, sanded and blended perfect. Looked fantastic and new after painting. But sure enough 6 months later there is rust bubbling back through

Is there a way you guys are able to fight this when doing cheap fiberglass/bondo filler work on rear quarter panels?

 

Maybe there's rust on the inside of the panel?
Perhaps some of that POR15 stuff would help
Always admired your user name
funny ****

 

Are you immediately painting the filler with a good catalyzed paint or primer?

If not moisture can get through and start rusting again...filler can be very porous.

 

^^^ good to know. How do you identify that kind of product at the store? Does it say that it's "catalyzed" on the label? And did you mean "catalyzed paint or catalyzed primer," or does regular primer give the same protection from moisture as catalyzed paint?

 

'Catalyzed' means that the paint or primer or whatever is a 2-part or 3-part mix. It's not just a solvent evaporating that cures the product, but a catalyzed chemical reaction.

Finish coatings that are just one part that you apply and then let dry can't create the same type of barrier that catalyzed products can. All of your real automotive paints are 2-part or 3-part....also called 2K and 3K.

 

sounds like you are just putting bondo on the hole? If you want it to last alittle while you need to use kitty hair bondo, it is water resistant and should last alittle longer. Are you leaving it with just primer on the surface?

 

Ya you have to use fiberglass filler 1st (which is waterproof and much stronger than regular filler), after grinding to bare metal. Then you put regular body filler then finish with putty.

some people use fiberglass on repairs that aren't even rusted, but they use it anyways to strengthen the repair. its good stuff.

 

I guess I went wrong simply using Rage as my only filler. I will try again using kitty hair as a base and finish with rage

 

That's the way to do it. I wouldn't say its much stronger but it will last longer and last a little longer. Just know you want to finish the bare metal in a 80 grit, and sand the kitty hair with a 80 grit (you can shape it with 36 but finish in 80. Bondo needs to be sanded in 80 and glaze sanded in 180.

 

Oh also finish the back side of the repair off with some kind of seal like seam seal, it will help water and moisture from getting back there.

 

try the new spray self etch primers, I know it's a spray can, but the stuff has gotten really good, self etch means it etches the bare metal to adhere. I do a lot of body work and I was surprised at how good the new ones really are, spray can doesn't necessarily mean junk anymore, the filler will actually adhere better to the primer once it's fully cured, just a little scuffing is all that's needed. The idea way would be to clean the metal to bare metal and apply a 2k epoxy primer, let it cure then fill, but you appear to be on a budget and the self etch will be fine

 

thanks guys, appreciate it. I plan on trying to get my old bondo work out this week

I will look for the self etch primer, do you prefer a certain brand?

 

I've had good luck with the duplicolor self etch primer