I've got some panels I picked up a few weeks ago that have spent years and years outside. The paint is long gone and they've become pitted and brittle, though the overall thickness is still there. The metal is workable. I've been working out some dents and reshaping the curves, but it's not easy going and I'm worried it'll work harden. I'm curious how people deal with the aged rusty metal. Should I apply some heat to the areas I want to work in an attempt to anneal it? What's a good technique to get all the rust out of the pitted surfaces? I've had to tack a couple of cracks along one edge and even at a low amperage it wanted to blow through. Any tips on welding this stuff? Thanks.
Hey, Try and do as much straightening as possible without heat. Any place you run into '' hard spots '' go ahead and use heat. A nice netural flame from a oxy/acc. torch works well, and it's not necessary to heat to a cherry red colour. Anywhere you have cracks in the metal will require that you weld these up, prior to compleation of your straightening. Now would be a good time to dump your ''squirtgun welder'' and take up gas welding. Gas welding produces a nice soft weld that is very controlable, and you can anneal the metal as you go. Too, you can produce repairs to panels that require little or no filler with a gas torch. Good luck, S****y Devils C.C. " It's time for another Tea Party !"
I sort of have the same problem with some of my stuff, I havent really hit it hard with any of those panels though. I will see how it goes at some point here! Good luck with yours!
Like I mentioned, I've been working the tin back into shape. So far it's moving where I want it to, but I can feel it harden up in places. I'll just keep working them and use the heat sparingly. I'll admit I've gotten lazy using the Mig over the last 10 years or so. I can't remember the last time I used the O/A rig for anything but heat or cutting.
The same with me. I haven't welded with O/A since High School Auto Body cl***. I have only used O/A for cutting and heating too. But I'm in the same boat with the thin brittle metal. Maybe it is time to put away my mig and fire up the O/A.
Weathering metal does not change the hardness, there is not enough temperature change to accomplish that. Heat (welding) or work hardening (hammering, bending, wheeling) will change hardness. Keep doin what yer doin/ remove rust before beating, so the oxidation contamination doesn't cause paint problems.
There has got to be something chemically going on with severely oxidized metal that contributes to the brittleness.
I don't know much, I'm just an Engineer in welding and metallurgy. Weathering / oxidation / rust on carbon steel WILL NOT internally harden the metal. Take care that the metal is a reasonably good grade of commercial steel, not some import junk of unknown composition. Remember the steel from Mexico made from radioactive s**** from dentists offices? Now Aluminum is another story. what makes Al attractive is that it does oxidize. A thin layer of Aluminum Oxide (sould familiar - sanding discs) forms on the exterior and seals the core metal from further corrosion. Which is why you must Stainless brush off the surface of Aluminum before Tig welding. The aluminum oxide has a much higher melt point than the aluminum a few micronds underneath. you blow right through the aluminum after the oxide layer
Treb is right, there is nothing metallurgically that changes due to exposure. The welding problems you are having is because it is thinner, and the surface rust (oxidation). The old panel you are working with has some cold working laready due to the forming that was done making the panel originally, but should still have plenty of working range before it gets too much cold worked. A slightly gas rich (also known as carburizing) flame will help deoxidize the surface when gas welding. I agree with the suggestion to use oxy-acet gas welding as easier on old thin rusted metal.
Those of us who don't have pristine metal to work with use what we have.i just had closed out that was typical Florida field rust;with about 4 inches of the bottom gone. a few sections had rusted thin. You shape a patch panel and work it in. I built a '34 ford 5 window that was the mate to this years ago and we replaced over 60% of the original metal,but I had a real steel body,not Tupperware. It all depends on your skill level and how bad you want it.
If you were to put it under a microscope in cross section, You would find that the rust goes clear through kinda like roots. What you are dealing with is weakness not brittleness. If you take a piece of it and clean it till it is spotless and run a mig weld on it you will get little spots of scale show up on the weld. This is the iron oxide that is in the metal floating out of the weld
very interesting. Do the rust neutralizers typically get down into those "roots", or is that something only a caustic bath takes care of?
Rust stoppers work by sealing the surface so air can't get to it, so, no more rusting. Rust converters do basically the same thing only chemically instead of mechanically. As far as a caustic bath, I don't know if it would get it all, but it would leave a converted seal down as far as it worked. I'm thinking your panels are like the floor pans in an old car. They may look intact with surface rust, but step on them ,there is nothing there. If you know a machinist with a comparator, clean of a piece of it and take a look at it. For comparison, do the same with some "new" steel.
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