> how to use an oxydizing flame to clean rust, please. I think that I have seen the results of that that I may have "accidentally" done without realizing what was going onoh sorry, missed that. yes you've already done it...it's just that simple...when you dial in enough O2 to make the green tips sharp (cutting tip), it's oxydizing...when you turn down the O2 to make shabby non-distinct green tips into what looks more like a welding flame and get the soot it's carbonizing. what happens is the rust will melt/blow off down to solid material long before the steel surface is effected.

>cleaning up a rusty piece of square tube 4 or 5 feet long instead of grinding it off. Could you then wipe it down with some paint thinner and a rag, let it dry and spray paint it with some rustoleum ? for that I would do a quick sanding disc to get some off, then use the torch for the pits...then a wire wheel...reason is it takes less gas (I'm miserly...maybe you aren't)...but I've seen fitters with an unlimited supply of gas clean big areas to new before slapping paint on. rustoleum is good, but it's just enamel based and armor coats only. there's a paint called POR (paint over rust) that is supposed to actually chemically bond to the rust and folks tell me (bus folks who aren't about to tackle years of serious rust on frames and such) it works impressively well, but I don't have any first hand experience with it...they say not to get it on your hands cause it won't clean off...it has to wear off.

re-reading your question, after the flame clean, sure... thinner and rustoleum, but there's a product called Ferrochrome (rust oxide colored emanel primer (Ditzler?) that I used to use with good results...they prime structural steel and bridges and such with it...and makes an excellent sandable filler/sealer/primer. if you see redish trusses or structural steel laying around a construction job, that's it. i used to use it on old cars...holds up well by itself, and takes an enamel overcoat perfect...which is where your pigmented rustoleum comes in. that's a finish you can leave outside in the weather.

another paint thought is rustoleum and auto enamels are pricey...go to a farm tractor dealer and get some machinery enamel...it's cheaper and better paint in my opinion...only downside is you're stuck with Allis Chalmers orange and white, or Ford blue, Deere green, Massey Grey ect...check out tractors and excavators that sit outside their whole lives to see the way that stuff holds up...it far outlasts rustoleum. it's been years since I bought some, but when car enamel was $75/gal. Allis Chalmers orange and white enamel was $35/gal. last car paint I bought was rediculous...like $45/qt.