1. On transformer tig welders, forgetting to set high frequency to continuous when tig welding aluminum …..

 this will result in the machine stuttering at low amperage because the alternating current will loose some of its half cycles when the direction of the current changes. Its pretty obvious and hard to miss. If the machine sounds like a Volkswagen with one spark plug wire missing, this is probably what it is.

2. Wrong size electrode … 

the electrode gets really hot at 250 amps on a/c. Using the same size tungsten as you would on DCEN does not work! The tip of the electrode will ball up and quiver and will eventually explode into your weld. Trying to weld beer cans with a 1/8” electrode is just as bad. The arc will wander and you will cuss.If tig welding aluminum is making you cuss, you are doing something wrong.

3. Wrong size filler rod …

too small a filler rod will result in the rod melting before it ever gets to the puddle. Too big a rod can actually block the shielding gas and will suck the heat right out of the puddle.

4. Cleaning aluminum with a carbon steel brush instead of using a stainless steel wire brush … 

every text book tells you to brush aluminum with a stainless steel brush dedicated for aluminum. The books are right on this one.

5. Too much torch angle …

 too much angle of the dangle will melt the filler metal and make it blob into the puddle. When you use the right torch angle which usually means only about 10 degrees tilt, the wire will feed into the puddle instead of blobbing.

6. Too long an arc see number 5…

you have got to find a sweet spot where your arc is close enough but not so close that you spend more time prepping electrodes than you do tig welding aluminum.

7. Too much argon on the torch ….

this one is subtle because most resources for tig welding aluminum recommend too much torch gas. If the arc is really noisy…like rattling your brains out, you probably have too much argon flow. For a 7/16” tig cup, you only need about 13-15 cfh depending on how far you have to extend the electrode. More torch gas is not better.

8. Not enough electrode stickout …

some manuals are just plain whack when it comes to electrode stickout. Hobart training manuals actually recommend only 1 to 1 ½ electrode diameters.! thats whack!!! If you can’t see the tip of the electrode, you can’t be sure your arc length is right. Right??Use this rule of thumb: Extend the electrode far enough to see the tip without getting a pinched nerve in your neck. No more than that.

9. Using pure tungsten ….

pure tungsten is is not that great. it balls up nicely but thats about all it has going for it. For years, textbooks have called for pure tungsten for tig welding aluminum. But pure tungsten often requires using a bigger electrode. And some inverter tig welders don‘’t like pure tungsten at all.If you want a good all purpose electrode , good for a/c and dcen. Get some 2% lanthanated...or the newer E3 electrodes.

10. Balling the electrode …

never “ball” the electrode. Just round it.. the ball shouldn’t resemble a monkey fist or tootsie roll pop. That ball makes the arc wander all around at low amperage. Who needs that?