I have some small rust holes I want to patch. I am going to try and do this thing properly so I don’t have to do it again. I plan on cutting out the rust and fitting a small piece of galvanized sheet metal and MIG welding it into place. I don’t have a welder so I am going to have to do the prep work myself and take it to a shop. I am going to have to drive it to have the welding done. I simply don’t have the money or the need to buy a welder.

What’s the best method for holding the patch pieces in place?

I was thinking of drilling holes around the perimeter of the hole and riveting in small tab peices. Then I would drill holes in the tabs I have created and in the patch and rivet the patch in flush with the surface. I can then drill out the rivets as the welding takes place.

Sort of what they show here: http://www.autobodystore.com/patch.htm

Any better ideas?

I would not fuss with using galvinized steel. When it is welded the galvinization will just burn off anyhow (and turn ya green if you breath it). I would just prep the pieces and know where they go. When you get to the shop they can just hold in in place and weld it right there. Good luck.

Cory

While that is a good idea, depending on where it is, the shop may be able to use vice grips to hold it in place with a small gap to fill. From what I hear this will give the cleanest weld and will be smoother than an overlap. On my car I did the overlap method, it looked like a big mess, but after tapping the weld in and a little bit of filler it now looks great.

Maybe I should mention that I already have bought the galvanized metal and the shop is a Do-It-Yourself shop and I will do the welding myself.

Do I need to grind off the galvanization around the edges?

no you don't need to grind off the galvanization. I worked for a welder who did chain link fencing. He used galvanized steel pipes all the time. Not once did he clean them off, also when you weld the stuff be careful. I know that working a weekend around the crap can make you very sick for the weekdays.

When Hk gets here he will give more advice.

As for doing it yourself, clamp it in place with a very small gap if you can. That way the weld will fill the tiny gap becoming smooth.

Also a note for doing it yourself. Keep it cool. Otherwise the metal may warp and you will need to fill it alot more than if you don't warp it. To do this just tack weld it in place, then do small welds about an inch apart. Go around the entire patch, leaving these gaps, then if the area where you started is cool, do it over again. You may possibly wanna go around two or three times to keep the metal cool. At least this is how me and my buddy did it on my car, and it turned out pretty good.

Can't clamp it. No access to the other side.

Pup, your wrong on the galvanization.

Asennad, you need ungalvanized metal. Not only with the galvanization contaminate the welds making it hard to get good tacks(more later), it is releases a poisonous gas that can make you ill. Just get another patch piece.

As for the tacks, you want to use one tack at a time like pup said, but go very slowly. I like to make sure I can touch the previous weld with my finger and not feel any heat before moving to the next one. If you use small tacks there is no heat in a matter of seconds as it disapates quickly. You want to use .023 MIG wire with shielding gas when welding FYI.

As for the patch itself, you want a butt weld with a hairline gap, maybe .025 or so. To hold it in place I would tack weld a piece of coat hanger or something to the patch. You can hold it in place to get it started witht the first tack, and push or pull with the coat hanger to line up the edges as you tack it in. Just grind off the hanger when it is tacked in place.

Last, take your time on the welding. It is not uncommon to spend several hours welding a patch if it is very big. You want to make sure and not get the panel hot at all.

Chris

[ March 31, 2003: Message edited by: TurboS10 ]</p>

I have welded in a heap of patch pannels made form galvanised sheet metal and never once have i experienced dramas. Because you are only doing small welds or tacks you aren't being exposed to enough of the toxin produced to give you any effects.

If the piece you were welding in formed part of the main structure of the car, like a firewall in a uni body car, you might go to the trouble of taking the gal of the metal as so it doesn't contaminate the weld, but for a simple patch, you will never notice any difference.

As for holding it in place, use a magnet if possible just to get the first tack on and then you can remove the magnet and do the other welds.

As far as MIG welding galvanized metal goes, the old wife's tale we were told in college (a hundred years ago in the early 70's) is that the cure for sickness from breathing zinc fumes is to drink milk, lots of it...
Moderm sheetmetal used in new car bodies is treated with a zinc coating, so it is weldable....but industry uses resistance welding mostly...