Problem wedling aluminum

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Hello all,I have been TIG welding aluminum for many years now.  This past week I ran into a problem that through me for a loop.  Out of the blue, every time I fire up my torch and start to lay a bead, the aluminum puddle goes into a state as if it were dirty and I'm trying to weld over the  oxide layer.I checked my hoses to see if maybe I had a gas leak but it's not leaking anywhere.  I tried changing out my tungsten thinking maybe my tungsten is contaminated and spitting out something that is causing this reaction, no dice.The only thing I can think of is that I recently changed out my bottle of argon.  The problem seems to have started about that time frame.  Is this possible?  Anyone else have this happen to them?Attached are a few pictures of what a tack looks like with some type of contamination present.  I have to "stab" the rod into the puddle as it is full of oxide floating on the surface.  I went out and restocked on stainless wire brushes thinking that maybe I contaminated the ones I use for aluminum so I got fresh ones.  Problem still present.  Tomorrow I am going to swap out the bottle with the one I carry on my portable rig as it was bought at a different location.I am at a loss.  Tomorrow I'll know if swapping the bottle solves the problem or not.Thanks,Tony Attached Images
Reply:I am interested in what you find out, concerning argon contamination. Especially, who the supplier was, if that turns out to be the case. Let's just say I know about a large scale argon contamination issue causing scrap wafers at a semiconductor company. Their problem also just happened recently.Lincoln Idealarc 250 (circa 1962)Lincoln Weldpak 155 w/Mig KitLincoln Squarewave TIG 175
Reply:Bad gas.
Reply:i would agree that it's probably mixed or contaminated bottle of gas. definitely looks like shielding problem. if the spare bottle does the same crank your pressure up or swap regs. are you cleaning the inside of the tube thoroughly also? could be drawing contaminants from there. some nice gaps till fill also.Last edited by jbmprods; 10-22-2011 at 03:36 AM.225NT bobcatAEAD200LEScott 125mm175, mm252 w 30A, PT225mm211, TA 181iHyper Therm 380, cut master 529100X & XX, Digital Elite6 Victor setssmith little torch, meco midget kalamazoo band sawsteel max saw evoulution circular saw
Reply:Just had the same problem with spool gun and millermatic 250 welding 1/2 inch aluminum trailer frame on semi trailer.  Tried everything, I had used the welder the night before at the shop with one bottle everything worked perfect, went to job sight and used the a bottle in welding trailer and looked like your weld.  Went back to shop and used original bottle everything worked perfect. Returned to job sight next day and finished job with shop bottle. The company was Air Gas.  Really thought I was loosing my mind when it was happening.  Put new bottle on and everything was fine.
Reply:I've had a similar problem with a new bottle being contaminated. Was TIG  welding mild steel and was getting a ton of porosity. Switched bottles and problem solved.
Reply:Thanks everyone for your replies.  I swapped out the bottle and it worked just fine.  The bad gas came from US Airweld.  The good one came from a local outfit called Verne Lewis.Attached are some shots I did quickly.  On the test plate you can see a bead run with the old argon bottle above (I wire brushed it as it had a lot of black inclusions before that) and one run with the swapped out bottle on the bottom, no touch up.I have to get this done withing a few hours.  I have about six joints to weld so I better get cracking.To answer any questions about the gap ahead of time, the client supplied the cut tubing.  He used a Dremel cutting disk, poor guy.  A lot of my clients are the do it yourself types (as am I) and like to do their own cutting ( some even fit and tack) then bring me their projects for welding out.Thanks all,Tony Attached Images