Hot Rods Rust

I've always been one to cut, weld, patch and fill over rust spots. And still think that way. But I've a job with a couple of tiny pin holes in a difficult area to patch. Yes, I realize that there is a possibly of more rust hidden inside. The rust occurred because the door sat on the bare ground for too long, latch side down. But it will be high and dry now.

Any success with rust patching dough like POR-15 or am I just wasting my time?

 

Do you plan on keeping the car, if so I would do it correctly. HRP

 

Rust can be like icebergs, only 10% of it shows...

 

I like that analogy.

 

Most rust " coverups" I've done over the years have lasted over 20 years , will you still be here in 20 years . POR 15 lasts for at least 10 uncovered , 20+ if painted . Its your time / money , if it works & looks good , why worry ?

 

That is a fact! The back side of that sheet metal with only a couple of pin holes showing on the front side, probably looks a lot like Swiss cheese on the back side.

Cover it with a rust converter and fill it with plastic is what is common these days. It looks Ok and may last a very long time and as long as the patched piece is not structurally needed, nothing is wrong with the idea, but if its ever in a wreck, it will have the strength of aluminum foil. Cut and weld in a new piece maintains the original structure. Your ride, your choice.

But, if you are brave and willing to take a chance, with a mig welder turned down pretty low and using a copper backer, you may be able to weld the pin holes closed. If you get lucky enough to weld the pin holes closed successfully, you will need to grind the outer surface of the spot welds with the edge of a cutoff wheel to bring the sheet metal surface back close to flat. Welding the pin holes only makes the patch as strong as the remaining sheet metal is.

My experiences tell me that most of the time you will likely end up with larger holes, but there have been a very few times I was able to weld the pin holes closed.

 

Depends on the desired outcome.

a beater driver/20 footer? Sure.

putting top shelf paint on it? Nope.

 

Ospho, get at Ace Hardware. Follow instructions. Spray mist will stain blacktop, cover with cardboard.

 

I've had good luck doing this a few times. I figure if I can zap the pinhole shut with the MIG welder and it doesn't blow a huge hole into the panel, it's probably OK. If the first tack or two just creates a bigger hole, then it probably needs to be cut out.

Same with sandblasting. I've beat on a few sheetmetal panels with a sandblaster and if they turn to lace, I figure the whole panel needs to be cut out, but if I only make a few holes and the rest holds up to the blaster, I'm OK to just weld up the holes.

Try it, see how it goes. There's always a balance. If I insisted on doing everything the 100% perfect way, I'd never get anything finished. But I don't want cobbled up garbage either. I wouldn't goop up a rust hole with POR15 or whatever. If it's totally cosmetic and you're not worried about it other than that, just fill it with kitty hair. If it's structural or might show later, at least try to weld it up.

 

Thanks guys. I'm gonna fix it right and forget the putty. It would probably work but I'm gonna weld them up after using a small hole saw and making a round patch to fit.

 

good call, I bet you will be happy you did.

 

I have used this technique on a beater. POR15. fiberglas cloth, alum bake pan. this is for work on the INSIDE of the panel. get some POR15 in the pan, add the fiberglas cloth (make sure you have enough cloth to cover the affected area), paint the area with POR 15, using gloves, apply the soaked fiberglas to the pinholed spot. let dry. it will last a long time

 

When you do it right let us know how bad it actually was.

 

I'm in the cut it out and replace it camp, but on the other hand I would imagine this car won't be driven in inclement weather and will be stored inside when not in use. If a converter product is used to treat the back side of the metal, how long will it take for the rust to get worse.

 

My 48 Plymouth coupe spent its entire life living outside in the north west corner of Illinois. There were rust holes in the roof big enough you could put your fingers through and not touch metal. I cut out the worst places and welded in patches. There were areas where there were a lot of rusty looking pits that you couldn't tell if there were holes or not, but the metal felt pretty solid. I cleaned those areas as best I could, and covered them with a rust converter (not POR 15, everything it touched failed within 2-3 years). Two coats of rust converter, following the directions on the converters container. After that I did a skim coat of filler and farm implement paint. I did nothing to the inside other then applying a peal and stick sound deadener (like, but not Kilmat).

That was back in 2011. The car still spent its life outside in the weather. In 2018, I did a repaint on the car (to automotive paint), so I sanded the areas a bit more where the rust pits were to have a better look. Most places looked the same as it did back in 2011, but two small places that were the worst back in 2011 (that probably should have been fixed back then), I did cut out and welded in patches. the remaining places I had used the rust converter on, I skimmed with filler and repainted the car. Other then being inside over one winter, the car still sits outside. Other then those two spots I patched, there are no other signs the rust pits have changed over 14 years of sitting outside in the weather.

 

I would also be curious to see this. Maybe take some before pics and some of the back sides of the plugs you cut out. Would be very informative.

 

I like to open the panel up by using tin snips or die grinder. I cut around the "problem" and inspect the back side of what I am cutting off. I keep cutting it bigger until the back side is good solid metal and all the rust is in the scrap metal bucket..