Solar Flux "B" works great. Mix into a paste (with something like isoypropyl alcohol), and apply (with a small brush) to the front, inside, and back side of parent metal joint, AND you might as well put some on your filler rod for good measure. It should weld nicely, with a very fluid puddle. (I actually think it welds more nicely than mild steel without any flux.) Use a standard (neutral, maybe slightly rich/excess acetylene as you want to stay away from oxidizing) flame.
Afterwards, plan on some removal of the flux residue, which will be hard an "glass like" where it got converted from heat. Flux that has not been heated sufficiently to "melt", will easily wipe / brush / wash away. Supposedly, a stainless steel passivation acid mixture can remove the glass-like solar flux residue, although I have not tried it for myself. (Solar flux literature recommends Bradford Derustit "wonder gel" product.) This has nitric acid in it, so may not be very easy to get a hold of.
I have used a stainless steel cup brush applied by HEAVY pressure and power by a large (7") angle grinder. In the process of removing the oxidation and flux, the power wire brush will kind of "smear" the surface of the stainless however. Also it will not be able to reach deep down into a crevise where the brush can not access.
The process isn't suitable for food grade or other applications, where the flux, or the flux residue itself could cause any problems. I have welded up a couple complete automotive mandrel bent exhaust systems with it however, works great.
Best of luck
Last edited by jakeru; 07-14-2011 at 07:04 PM.
'13 Everlast 255EXT
'07 Everlast Super200P
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