I am going to rebuild the seat springs on my Suburban, using a somewhat rusty donor seat for springs and parts. There are small coil springs in "X"s tying the seat coils together to distribute the loads. On my donor, these small springs are rusty. There are also long, straight springs going across the seat bottom, and I need a few of those as donors too. I had some of these small springs sand blasted when another seat frame was done, and the small springs became brittle. I believe the sand blasting took the temper out of them. I'm looking for a way to clean these donor springs, and am thinking of dipping, or perhaps tumbling. I'm concerned that dipping them in acid will cause hydrogen embrittlement, as might electrolysis. What is the chemical reaction with moll***is (sp?) that causes metal parts to lose their rust? It's important to me that the springs are clean and rust free, but they also have to retain their temper. Any ideas? -Brad
What about sandblasting? I sandblasted the springs of my T Roadster and nickelplated them after the sandstorm. A little bit of polishing and they look like bare metal.....
I have derusted much smaller springs with phosphoric acid based products. Results were clean springs that snapped at first pull. These were things like clutch pedal return springs, and they seemed to have good strength and springiness before their swim. Maybe someone here can provide a better answer, but my tendency without further knowledge would be to paint them with some sort of rust encapsulator.
I'm no metalurist but I've done my share of electrolysis and love it. However, I wouldn't do it for springs! I'd try that Safest Rust Remover or Evapo-Rust first. This stuff works in a few hours of setting. I've never had it damage springs in the tools I've done. It's really amazing. No I do NOT sell it.. just really like it. I've used CLR too, overnight, with great results. But no matter if you use it or mol***es, try it out on an old spring from something else first!!!!!!! There's no going back... Let us know how it goes, please.
Are they hard to find? . The rust is the problem,not the method used to clean them. the microscopic holes in the spring surface are stress risers and once the spring has to work with a person on them and the vibrations from a car going along the road,they will snap. Spring steel is not ductile in the fashion of mild steel. That is how it retains it's "spring" so once a mark or scratch is made the normal working of the spring causes the mark to become the start of a fracture. Unless you want to spend time with fine emory cloth polishing the springs to remove all marks your only option is to get new springs wound if none are available new ( a business venture for you?) . A cl***ic example is MOPAR torsion bars,they will break at the point where a rock has hit them and marked the surface.
Hydrogen embrittlement does not occure in chemical stripping. It happens during the baking process of a part, after it gets a finish coating applied to it.
Brad, I have used mol***es for much derusting. It has been my understanding that the solution is slightly acidic, but does not attack steel or cast iron. I also use electrolyses, but hydrogen is a byproduct of that procedure. Electrolyses might be a problem on your springs. I mix my "brew" at 4 parts water to one part mol***es. I put my tub on sawhorses and place a small heat lamp to warm it to 85 degrees. Works great.......but somewhat slow. Figure a week or more for great derusting.
what about citric acid, might work for seat springs http://www.jalopyjournal.com/forum/showthread.php?t=248848&highlight=citric+acid
All derusting solutions share the same problem when it comes to flexible metal. They attack the grain boundaries, and because it's already corroded, the attack is allowed to go deep. Personally, I'd knock the chunks off em with a combination of wash & scotchbrite then brush/dip heavy paint to seal it all in. Rustoleum or POR15, that kinda thing. Cause after all, they're in a seat. They don't need to be finished like a fender. You just wanna eliminate rust chunks floating in the foam and seal the metal back up. good luck
I used Oxalic acid to derust a stained headlight surround with three small springs in them and they seem fine. Here's the thread where I did it. http://www.jalopyjournal.com/forum/showthread.php?t=248198&highlight=oxalic+acid I use this stuff all the time and haven't had much problem with it but I haven't derusted alot of springs.
+1 for Evapo-Rust. It does not affect iron, only iron oxide. Closest thing to magic I've ever seen. If you think Hydrogen embrittlement is a problem, bake the parts at 300° F for 12 hours immediately after the treatment you are giving the parts. That's what is done to critical parts and springs after plating, it forces the hydrogen out before it can damage the steel.
He is talking about seats, and the smaller springs, clips etc. that make up the cushion and backrest ***emblies, not suspension springs.
When blasting, you actually work the surface of the metal with a hammering/smearing action. One of the reason surfaces look so good is that pits can have nearby metal rolled over the top. On a large suspension spring with careful blasting this is not such an issue. On a small spring it's a major issue because the affected layer is a large % of the spring's cross section. That worked/hardened/smeared layer is the same thickness if you're blasting 1/2" thick steel, or 1/32" thick steel (***uming gun settings the same).
Brad: I will Email a PDF that explains a bake out to help with the HE. The HE happens during the cleaning process and it can happen to different degrees depending on the type of material you are cleaning and the process. If you have a member Engineering bud he can get you some ASTM's for ref. material to help you figure out a process that should work for you. Good luck with your build. It sounds like you are very thorough. I could not add the PDF here as it was to big for the Hamb upload.
Thanks VERY much for all the info! I really appreciate it. I also like that most of the guys who replied actually get what I'm doing! Yeah, they're inside the seat, and nobody will see them, but it's really, really important to me that the seat be factory perfect. There is nothing worse than driving 20,000 miles a year in someone else's ***-dent. I restored the rear seat, with fresh springs taken from a clean donor, and it's like riding on the couch. That one is when I realized blasting the small springs made them all brittle. The bigger coils were fine, but the little ones were all junk. The little springs are too small to hand-detail, but the others could be done with scotch-brite and POR15 as suggested. However, I also like the idea of the Evapo-rust and mol***es. Thanks for all the tips everyone. -Brad
I really don't think you're going to like any soak. It's not just hydrogen embrittlement. See here's the deal, any soak will remove the metal's natural protective oxide layer. All old metals have them to some extent or another. Even steel. Ever buffed an old chalky paint job and were left with a shiny car with a super-thin layer of paint? That's what's gonna happen when you soak in any oxide attacking solution. Except with the metal, that paint layer surrounds individual grains. The solution goes after the grains, and because of the flexing action of old spring steel, it goes deep because those grain boundries have been mechanically loosened. Everywhere it goes deep you lose cross section. Lineup 2 bad spots and suddenly the spring won't take any tension. Snap. This is probably a case where perfection might be a detriment. good luck
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