Amateur Rust Repair... need advice keeping the rust out (no 56k if anyone still has that)

Hi guys

Well, I finally got my car sorted a few weeks ago and took it to fill it up, but had only been using 1 hood pin because I was lazy and planned on driving slow. Well, long story short my hood flew up and broke my windshield. So, I had rust under there at the base of the dash that I couldn't get to unless the windshield was out... so I thought it was a good time to address it. And, while I'm addressing the rust there, I may as well get the rust everywhere else. It ended up there was more than I thought!

Anyhow, I just sort of jumped into it... I didn't have any experience or anything. Since I'm borrowing a mig welder and have scrap sheetmetal from the bent hood, I figured I'd cut out the sections and weld in similarly shaped cuts of sheet metal. It didn't take long to realize I was going to have to spot weld it around and did some searching and apparently that's the standard procedure. The next thing I learned was to cut the patches as close to the original shape as possible, and hence my 2nd repair is considerably more beautiful than my 1st, which you can't really see anyways.

So, another problem I was running into are places that had what appeared to be exfoliation corrosion... and I couldn't tell where it stopped rusting (because the metal was peeling). I found more places like that after I had already made repairs there. Am I going to have to go back in and cut deeper or will rust converter+primer+paint kill it?

Well, after I had most of the repairs done (or atleast covered in primer) I went on vacation for 2 weeks. Well, I just got back and I can already see rust eating through the primer in some spots. I did wirebrush both sides of all the patches as well as around the cutout areas, but I couldn't really get to the inside.

I sprayed as much kleen-strip rust converter in there as I could and then on the front as well, followed by rustoleum primer, and well, here are the pics.

My wonderful workbench!

Sample Patch (I doubled over on one side that is 2 sheets thick on the car, everywhere else was only 1)

Fitted

Welded

This was my 2nd ever repair after being ground down

Fender comparison. The non-rust fender was already bent when I acquired the car, and the rusty fender isn't bent

Fitted

Welded

Hatch repair. This one was really tough because the bottom line is curved and I really had no reference to where the corner was supposed to be. After thinking about it for a while... I extended the lines to make imaginary cornerpoints on the good side of the hatch, measured that distance, then extended the lines to make an imaginary corner on the top of the bad side, and brought it down that distance to find where the imaginary corner would be where I had nothing to work with, then made a frame from there.

Frame

Welded

Another angle

So, that's where I was at when I left. I covered it in primer and was going to fiberglass in the actual curved corner there.

Here's what I had when I got back 2 weeks later!

This one was funny when I was doing it... because the other side had a huge rust hole, and this one had like 1 little rust crack. I ended up fulling a fist-sized chunk of bondo out of this, as well as probably 1 brown-paper bag's worth of brown paper used I'm sure to support the half-can of bondo while it set. Gotta love PO's!!!

This was the other side that was obviously bad. Actually, one side of this repair came unwelded due to that corroded half-metal crap... obviously not good so I'm going back in for this one.

So... I'm pretty sure that's not good. I wouldn't want to put nice paint over that and just have it rust up again, so does anyone here with experience with this have any advice for me? Also, if you see anything bad about any of the repairs please let me know.

Sell car, buy unrusted car. It's sad but true.

I'd practice that welding a bit, errr, a lot more.

joshx99 wrote: Sell car, buy unrusted car. It's sad but true.

Yup.........tend to agree. Sometimes you gotta know when to fold em.

Wait but... they're all just like little spots. There's nothing big on the unibody, just little cosmetic stuff...

Okay, well I'm not doing that either way. If I have to I'll cut out all my 'repairs' and fiberglass them.

As far as the welding... I was using the car for practice! I mean, it's all getting ground down anyhow...

Hey, the most finished thing I've welded is some floor pans. They weren't pretty but they were strong. You need to get the weld pool deeper into the metal; it's beading up on the surface and that means you're not getting good penetration. [edit: you might need to turn the power level up a little. But not too much or it will warp!] Once you tack the piece in place, you should go back over it in a smooth, end-to-end run, unless it starts to warp, then you have to do it an inch at a time. (Pain in the ass!) But regardless, you want the finished weld to be continuous, not gapped like the finished welds you have there.

I am by no means an expert; I'd just recommend getting an auto body welding book. I agree with you that you should keep going - how else are you going to learn??

Oh, also, make sure there's no rust and no paint around where you're welding. You'll get foreign matter inclusion in the weld which makes a weak weld prone to corrosion.

I think your welds rusted so quickly because the primer wasn't thick enough or thorough enough. Was it parked outside or in an open / damp enclosure?

Thanks for the input. I didn't know it was so important to have the repair continuous.. it wouldn't be too hard to go back and fix most of the spots. There are some gaps however that are pretty big but too small to add more metal. Actually, that's what a lot of those welds that appear they haven't penetrated are, I was trying to build up on the edges and bridge the gap.

As far as the power, it was burning through instantly at some places even on the lowest setting. I realized that if I upped wirespeed I can combat that sometimes but it didn't help everywhere..

Also... again, there is like... primer on the inside that I can't really get off, and it's probably getting into the welds a little. How prone to rust does that make it? I'm not concerned about strength anywhere except maybe the hatch but I can get to that on both sides to clean it.

you're using a flux core mig for thin sheetmetal. that's tough to do well. use thicker pieces of "patch" metal as they'll help absorb some more of the heat so you won't have to go as fast. you say you were burning through but it looks like you have very little penetration for most of your "spots". add just a little heat and a little more wirespeed. at this point, i'd plan on cutting out those patches and starting fresh with a thicker piece like i said. remember that you want to give it just a bit of time at first to start the pool, then draw it down the weld line. oh ya, that's probably part of the problem as well. it looks like you've got a pretty big gap between the patch and the old metal. i bet as soon as you get the pool to the right point, it ends up just dropping through because there isn't enough of the metal on either side to pull in. a little bit more snug fit would help there as well. i learned the same way you did so if anyone else with some more knowledge/experience than me wants to chime in and clarify/fix what i've said, please do.

you're doing well! keep going! don't be afraid to cut out and redo!

Holy jeebus.... CLEAN your weld areas! Front and back of every side should be clean bare metal w/in 1" of the weld. What size wire are you using? If you can convert to gas, you'll be ahead of the game, but I'd use about .023 wire max. It's also very difficult to do a butt weld patch panel. Buy a cheap flanger tool and use it. That way you're actually welding two layers instead of trying to jump an air gap.

You made matters hard on yourself where you chose to seam the fender. Its going to be difficult for you to grind it flat and fill the area leaving no trace. Next time you might consider making the patch larger, even if it means sacrificing some good metal, to make the repair easier to access, smooth and blend.

That doesn't look all that bad, nothing a little grinding/bondo/paint can't fix.

And when you've had it with it just do something like this:

http://gilesprojectcar.blogspot.com/search/label/Mid7%20Spaceframe%20Fabrication

...and the Suzuki Swift link on that page under the Links section to the right.

http://archive.grassrootsmotorsports.com/board/viewtopic.php?id=26460

go down almost to the bottom of the page, i can get you more pics. i did that repair butting to clean metal with a flux core welder and .035" wire. granted my dad is a retired trained professional certified in all kinds of welding and taught me everything i know about it, but it can be done.

the biggest part is getting out to clean metal, cleaning all contaminants away from the repair, and getting a nice solid fit on the joint. after i made my template(pizza box = perfect) i made my patch a hair larger and ground it down to exact.

Don't get discouraged, everyone starts somewhere. The biggest thing is to be patient. Take your time, don't rush. The advice on doing the work is straight on...grind out to solid, clean metal before attempting to weld in a patch. Bondo will cover a multitude of sins, but you want to keep it to a minimum. You might want to POR15(or similar) the rust to keep it from spreading. Just keep at it and learn as you go. Hey, it's not a show car. besides, when you're done someone from the north will buy it- they're always looking for Florida cars!

Primer is porous. It soaks up moisture and makes things rust unless it is coverd in paint. When you meld steel, the surface wants to oxidize (rust) important to get a wire wheel over all the welds and then prime and paint.

I note that the welds are getting better as you go. I would add a bit more heat to the rig for better weld penetration and a flatter bead.

Also make sure you clean the welds really well. Get some small brass brushes and scrub the crap out of them, the flux will make stuff rust. Steel brushes will leave steel particles that, well, rust.

Once wire brushed, wipe them down with lacquer thinner and as soon as they are dry hit them with some spray bomb primer and then some cheap spray bomb paint. That should hold the rust monster at bay until you can finish the bodywork. Once you are ready for the real paint, the cheap stuff will come right off with more lacquer thinner.

It looks like you aren't using any gas...that gas will make a HUGE difference. Are you using gas? As others said, you're also dealing with lots of contamination and you're not getting enough penetration. It's tough with thin sheet metal, see what wire size you're using also. If your wire is too big it'll take a ton of heat to melt it (compared to the sheet metal) so you'll just blast through the sheet metal when your wire actually melts.

Practice on some more scrap metal that's the same thickness before doing more on the car. When you've got things right you should be able to weld a continuous bead and make it sound like bacon sizzling. A good, constant sizzle is what you're going for. When you can get a weld that sounds good and LOOKS like a weld is supposed to without grinding, then you've got your heat/gas/wire speed/technique/prep dialed in. Then give it a try on the car again. SImilar to most things, getting the basics down solid is the most important part, once you know how to dial in your heat/wire speed, etc. and your equipment is set up with the right gas, wire size, etc. then doing advanced sheet metal work will be a heck of a lot easier than if you're still working on the basics of technique/set up.

Good luck! Rust repair is a real PITA, but if you're really in love with the car for sentimental reasons then it's pretty rewarding to bring it back to life. As others said, if it's not for sentimental or education reasons, rust repair isn't worth the hassle...it's much easier/cheaper/faster/better to get a car that isn't rusty.

Bryce

some guys have had success with adding a rheostat in the power cord, or just using 25ft or 50ft extension cords to lower the voltage to the welder. Check out what this guy has done over on the volksrodders forum:

http://www.volksrods.com/forum/showthread.php?t=7172&highlight=rheostat

scroll down to post #28

Classic MS had an article with door repair on the Modern Midget which described a method called 'stack the tacks'. You basically skip around, placing tacks on the seam in a semi random order, starting out with the tack welds about 1" apart. Then you skip around your patch seam until you have filled the whole seam. You then grind the tops of the tacks flat, again skipping around. That way you don't build up a lot of heat, which is what warps sheet metal. You still have to wire brush and clean the ground off welds really good, particularly with flux core. I have done this recently with flux core with good results.

It looks like you did this with your hatch repair, except you didn't grind and clean.

EDIT: I just remembered something. That spray bomb rust converter stuff will actually start rust on bare metal. That happened with my 914, I thought I was doing good by spraying a big part of one fender after sanding the paint off. It started surface rust all over.

Yeah... that stupid chemical may not have been the way to go.

Anyhow, thanks for the input everyone. I ended up doing what I could with the MIG flux core .030, grinding, blending, and priming. I still have 2 repairs to blend for now