DIY Welding on rusty rocker panel?

[14W]

Hi.

So i noticed this winter left me with a nice surprise on my right rocker which is that the front part had rusted through. The rust is only on the bottom exterior part,the inside has no rust yet. I think this is actually my fault bcs car was damaged there and then i resprayed it kinda in a hurry, so i didn't do adequate job with the compressor but i just rattle canned it and put the chore on do it later list. This is also the only rust issue on my car.

So i am thinking of buying a new e39 or to try to repair this at least semi properly via cutting the rust out and weld the new metal in and then fill/repaint the whole thing. I don't wanna fiberglass or styrofoam patch it.

I have a question if such of a job is even plausible to succeed ,since i have no experience in welding whatsoever and i have yet to buy a welder too? I know how to do paintjobs on cars and have tools for it though. Did anyone do this kind of thing on their own?

If that is possible what kind of welder and metal do i need? I would prefer to buy a used stick welding machine over the MIG bcs of the portability and off course the price is important too. Hope this isn't a stupid question ,but like i said i know nothing on this topic yet. But i always wanted to have a welder and learn this skill-set and i think this might be a fun project to start. Bcs if i learn welding there is almost nothing I can't DIY on cars.

Hope this post serves as a lesson for you all too : do not neglect "small" issues thinking "yeah i'll do this next year" , bcs stuff like this is what happens.

Tnx.

[BimmrMeUpSnotty]

Stick welder over MIG..... Do you self a favor, get the stick welder out of your head, get a good 240 volt MIG with the gas lines so that you can shield h weld properly. When you get one, don't get carried away and start on the car, go to a body shop, ask if you can have a few wrecked fenders, a door, and hopefully some thick scrap metal, the different thicknesses will teach you how to control the heat settings, on the welder, that would be heat setting, and wire speed settings, also the amount of shielding gas to use. Bone up on your welding skills before you do any welding on the car.

The car, you want to stop the rust, that means grinding the paint out of the way, wire wheel the rust off the metal, see if it goes all the way through. A product called POR15, black or grey, your choice, same thing, stops the rust. Brush it on over the affected metal. It dries very fast, levels out into a nice smooth coating of primer. Read the label. Don't get a big can, get a few pint size cans, they are about $25 a pint, once you open the can, use it, as what is not used, will already start drying up and hardening in the can. It's probably good for a couple days, read a he label. If the rust went all the way through, I would cut out the bad metal, and then new metal needs to get welded in. If you don't know how to weld, you will punch holes, not get the material hot enough, secret to a good weld, clean the metal involved, the correct settings on the welder, the right amount of shielding gas, if it is sizzling on like bacon, you've got the hang of it, and the right amount of heat is being applied. If it's farting and popping all over the place, you're doing it wrong, lots of grinding will be needed, the weld will be porous, your weld sucks, you suck.
So, practice on the scrap metal, different thicknesses, before you hit the car, but stop the rust with the POR15 right away.

After welding, you need to address the bare metal inside of the rocker.... Use the holes for the doorway step pads, you have to spray liberal amounts of inner cavity wax, SEM makes a decent wax that can be sprayed in there, but if you want the same stuff that the factories use, get the stuff from Wurth, it's good stuff from the fatherland. Good luck.

[JimLev]

If you've never welded before I'd get a MIG and do a lot of practicing before attempting any welding on the car.

[BimmrMeUpSnotty]

Hey Jim! We're on like Donkey Kong!

[JimLev]

Hey Jim! We're on like Donkey Kong!

Ha, I must have been typing just as you posted.
A stick welder would probably blow holes thru that metal.
Stick would be good for 1/4" steel plate not body sheet metal.

[14W]

Stick welder over MIG..... Do you self a favor, get the stick welder out of your head, get a good 240 volt MIG with the gas lines so that you can shield h weld properly. When you get one, don't get carried away and start on the car, go to a body shop, ask if you can have a few wrecked fenders, a door, and hopefully some thick scrap metal, the different thicknesses will teach you how to control the heat settings, on the welder, that would be heat setting, and wire speed settings, also the amount of shielding gas to use. Bone up on your welding skills before you do any welding on the car.

The car, you want to stop the rust, that means grinding the paint out of the way, wire wheel the rust off the metal, see if it goes all the way through. A product called POR15, black or grey, your choice, same thing, stops the rust. Brush it on over the affected metal. It dries very fast, levels out into a nice smooth coating of primer. Read the label. Don't get a big can, get a few pint size cans, they are about $25 a pint, once you open the can, use it, as what is not used, will already start drying up and
hardening in the can. It's probably good for a couple days, read a he label. If the rust went all the way through, I would cut out the bad metal, and then new metal needs to get welded in. If you don't know how to weld, you will punch holes, not get the material hot enough, secret to a good weld, clean the metal involved, the correct settings on the welder, the right amount of shielding gas, if it is sizzling on like bacon, you've got the hang of it, and the right amount of heat is being applied. If it's farting and popping all over the place, you're doing it wrong, lots of grinding will be needed, the weld will be porous, your weld sucks, you suck.
So, practice on the scrap metal, different thicknesses, before you hit the car, but stop the rust with the POR15 right away.

After welding, you need to address the bare metal inside of the rocker.... Use the holes for the doorway step pads, you have to spray liberal amounts of inner cavity wax, SEM makes a decent wax that can be sprayed in there, but if you want the same stuff that the factories use, get the stuff from Wurth, it's good stuff from the fatherland. Good luck.

Tnx for the detailed answer, yeah if that's the case i don't have a choice but to buy a MIG. I knew that MIG is better for beginners and thin metal, but had no clue that it's such of a difference. I was thinking on practicing on a scrap metal first off course. I didn't know about POR15 glad you mentioned it.

"Good luck." Yeah i am gonna need it, if I am gonna to tackle this nightmare. Gotta find some good learning vids, and i am gonna buy some welding textbook too first.

[JimLev]

Don't forget you'll need a bottle of shield gas too.
Probably something like 75% argon 25% CO2.
Snotty, you probably have done a ton more MIG'in than I.
I'm a sloppy TIG guy, 100% argon.

[14W]

Don't forget you'll need a bottle of shield gas too.
Probably something like 75% argon 25% CO2.
Snotty, you probably have done a ton more MIG'in than I.
I'm a sloppy TIG guy, 100% argon.

What is the shield gas? Is that the gas which the welder needs or is it some other gas? Yeah I really need to find myself some welding 101 material before, I do anything, bcs i was just looking at site similar to US craiglist and have no idea what I even need. What's the difference between TIG and MIG? Bcs I noticed that the TIG welders are cheaper and look smaller than MIG's . Do you maybe know about the masks? Are those auto-dimming masks safe ,or can they fail ,and it's safer to buy a "normal" mask?

[JimLev]

You may be better off taking it somewhere and having it done unless you really want to learn and spend about $1000 to get started.
Both TIG and MIG need a shield gas so the weld doesn't get contaminated.
MIG feeds the wire out, TIG you hold the welding rod in one hand and the TIG torch in the other.
TIG is capable of better welds than MIG but costs more.
I use an auto darkening helmut.
You can buy a MIG setup that doesn't need a shield gas but the weld splatter is pretty bad. It uses wire that has a flux core.
Spend a little time on YouTube. There are a lot of good guys showing how to weld.

[dwgates]

It's also nice to have an inside place to weld if you're using gas. Otherwise your welds may be at the mercy of the wind while you're welding. Of course you need to have some place where sparks aren't going to set your inside welding area on fire. I'm not sure on these cars if you have to do anything more than disconnect the battery to do any kind of arc welding (stick, MIG, or TIG) to make sure computers on board are safe. You might want to see if anyone has BMW specific cautions there.

[14W]

It's also nice to have an inside place to weld if you're using gas. Otherwise your welds may be at the mercy of the wind while you're welding. Of course you need to have some place where sparks aren't going to set your inside welding area on fire. I'm not sure on these cars if you have to do anything more than disconnect the battery to do any kind of arc welding (stick, MIG, or TIG) to make sure computers on board are safe. You might want to see if anyone has BMW specific cautions there.

Yeah at least the place isn't an issue as i have a quite big garage with a pit and a work table with tools suitable for metallurgy. I was thinking of the electric shock of the ECU and modules issue too and have yet to find out. I remember when I had my catalytic converter replaced they only disconnected the battery and it was all OK.

[BimmrMeUpSnotty]

All you have to do is disconnect the negative cable, nothing special. For your workspace, sweep the floor, pick up combustible material off the floor, you’d be amazed what a rogue cherryball can do on the other side of the room. You also need to remove anything combustible in the car that is in the direct vicinity of where you are going to be welding. Have an extinguisher handy nearby. When done welding, it is good practice to stay in the area for at least 15 mins, to make sure nothing ignites in the car, and in the shop. On welding helmets, get a good one with a big viewing window. The more sensitive the auto damage meaning screen, the more expensive, same with the ones with larger windows. I got a way overpriced one from SnapOn, sure it was overpriced, but who cares, it is damn good, on sale, I got it for over $400, you should be able to get a decent one from Lincoln, probably around $150 to $250. The ones from Harbor Freight, junk, it’s up to you, how much do you value your eyesight? You get what you pay for.