cleaning sheet aluminum of paint, jb weld, silicone

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just a quick question:  You should use a stainless steel brush to prep aluminum. But,  for the first few passes to remove most of the mess, will a low carbon brush work?   Is it a good plan, or am I making more work for myself?-thanks
Reply:Really, I am also wondering the reason why a stainless brush must be used....or is it urban legend to sell brushes?The process is unspecified. TIG, MIG, or O/A. Maybe a combination of all
Reply:You can use a sandpaper wheel on your angle grinder to get through the big nastiness, then finish up with a stainless wire brush and acetone.MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:"The oxides, if not removed will contaminate the weld." A quote from someone here. "Oxides" are like rust? White rust.
Reply:Does a steel brush cause oxides or some other bad thing?I would think that the glue and sand would also leave a mess...but it is my ignorance that keeps my talking.
Reply:Originally Posted by DesertRider33You can use a sandpaper wheel on your angle grinder to
Reply:Careful not to feather edge the basemetal. Most of the alum on a boat is pretty thin.As far as the wire brush.............. I have a practice coupon here on my desk, with about 25" of bead. It's four pieces 2" wide by 8" long strips of 1/16" alum, welded to make a 2" x 2" x 8" box. I used the class shop's bench powered 10" carbon wire brush to remove the oxide coating, some of which took quite a bit of pressure to start cutting the surface oxide. These brushes are used to clean almost every mild steel weld made in class. So, that's 64" of cleaned alum. The end crater of one weld has a bleed of rust, half the size of a Q-Tip. That's about 40 welds on the outside corners (practicing my starts). YMMVOnce upon a time, I was overly concerned about alum prep. Not so much any more. IMHOFWIW: OLD Miller Syncrowave 250, balance set at the high end of the 'balance' stencil; 3, I think. Normally I'd let the AC+ do the oxide cleaning, but I wanted the edges to puddle freely for my first tack weld practice without filler. This week I'll be doing no cleaning and see what happens.  (no JB Weld or silicone )9-11-2001......We Will Never ForgetRetired desk jockey. Hobby weldor with a little training. Craftsman O/A---Flat, Vert, Ovhd, Horz. Miller Syncrowave 250
Reply:In theory you will embed steel particles in the alum that will contaminate and cause issues in the weld. Alum oxide sand paper will do the same thing. However if you are not doing aerospace work, this minor contamination may or may not be an issue. I generally error on the side of being more careful than less in weld prep.One thing I have found with wire wheels and glue or adhesives. You will frequently smear them on the surface causing a bigger problem. Jb weld will most likely soften with acetone,  methyl ethyl ketone or another solvent. Silicone just plain sucks to remove. Wire wheels don't do much often with silicone as the silicone just flex's rather than cuts. Also a steel cup wheel is Very aggressive on alum. On a thin boat skin I can see you doing more damage than good with one unless you are VERY careful.
Reply:Originally Posted by DSW Silicone just plain sucks to remove. Wire wheels don't do much often with silicone as the silicone just flex's rather than cuts.
Reply:FWIW:Well, a couple of days ago I shot off my mouth about using the shop's carbon wire brushes for cutting the oxides off of alum. I said that I had one rust bleed. Well, tonight, I have a another one. This happened sitting on my desk, here in Colorado; where humidity is never a problem. In class it doesn't matter, I'm just learning the alum process. But it does introduce carbon (rust) into the bead, 9-11-2001......We Will Never ForgetRetired desk jockey. Hobby weldor with a little training. Craftsman O/A---Flat, Vert, Ovhd, Horz. Miller Syncrowave 250