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10 Common TIG Problems and Solutions

Here are some descriptions of common TIG mistakes and basic tips on how to prevent these errors from happening.

Figure 1. Poor gas coverage leds to contamination.
Figure 2A. Aluminum welded in DC with argon.
Figure 2B. Ideal aluminum weld.
Figure 2C. AC balance set too high.
Figure 2D. Balled tungsten.
Figure 3. Grainy aluminum weld.
Figure 4. Lack of fusion in the root #2.
Figure 5A. Poorly filled weld craters.
Figure 5B. Weld crater filled.
Figure 6A. Uncleaned steel weld.
Figure 6B. Clean steel weld #2.
Figure 6C. Uncleaned Chrome Moly.
Figure 6D. Cleaned chrome moly.
Figure 7A. Poor color on stainless steel.
Figure 7B. Good color on stainless steel.
Figure 8. Sugaring on stainless steel.
Figure 9A. Excessive amperage-heat input.
Figure 10. Change in arc length 1.

Gas tungsten arc welding (GTAW), also known as TIG, is arguably the most difficult process to learn. This article contains descriptions of common TIG mistakes and basic tips on how to prevent these errors from happening.

Throughout this discussion, please reference the application photos to the right beginning with Figure 1. Weld contamination can occur when shielding gas is not turned on, there is too little or too much gas shielding or the gas is blown away. To troubleshoot gas contamination issues:

(1)  Check the gas cylinder label to make sure you’re using the right type of gas for TIG welding (generally 100 percent argon, or an argon/helium mix for aluminum)

(2)  Set the proper gas flow rate, which should be 15 to 20 cubic ft per hour (cfh). Excessive gas flow creates turbulence and swirling currents that pull in airborne contaminants and cause arc wandering. Not enough provides poor coverage of the weld.

(3)  Consider using a gas lens instead of the standard collet body to provide better gas shielding.

(4)  Check all fittings and hoses for leaks. Use a gas leak detection fluid, available at most welding suppliers, over the hose and all fittings. If bubbles form, you have a leak and need to replace defective components.

(5)  If everything else checks out, you may have moisture in your tank. This doesn’t happen often – check with your gas supplier.

You should generally always TIG-weld aluminum with alternating current (AC). Welding with direct current (DC) will make it difficult to eliminate the aluminum oxide layer. This oxide layer can mix with the filler metal, contributing to contamination.

–  The electrode positive (EP) portion of the AC cycle etches away the oxide, while the electrode negative (EN) portion melts the base metal. AC balance control allows the operator to tailor that balance to the weld. Brown or black oxidation or flakes in the weld puddle can be eliminated with increased EP. Too much EP, conversely, balls the tungsten and causes excessive etching.

–  Only start welding once the puddle has a shiny appearance. This is how you know the oxide is removed and you are ready to add filler metal.

The grainy appearance of the weld bead is typically caused by welding too hot causing too much base metal dilution.

(1)  Find that “sweet spot” that is not too hot and not too cold, and this graininess will go away.

(2)  You may have the wrong type of filler metal (4043 instead of 5356).

(3)  Always remove all grease, oil, and moisture from the filler and base metal.

Lack of fusion at the root of a T-joint or a fillet weld can be caused by a number of factors: improper fit-up, holding the torch too far away from the joint (increasing arc length) and improperly feeding the filler rod, to name a few.

(a)  Reducing arc length will provide better directional control and help increase penetration. It is also important not to under-fill the joint or weld too quickly.

(b)  Inverter-based power sources offer greater control over arc performance allowing you to tailor the arc to be more focused into the puddle.

Craters occur at the end of the weld and lead to cracking. Causes include instantly dropping the weld power and removing the filler rod too quickly. Adjust your technique and continue to feed the filler rod while slowly reducing current at the end to fill in the crater. Using a TIG welder with a “crater control” function may also help.

All base and filler metals need to be cleaned, whether it’s mill scale, oxide on aluminum, or dirt and grease. Grind, brush and wipe away all potential contaminants. For cleaning aluminum, dedicate a stainless steel brush to the task to prevent contamination from other metals. Never use brake cleaner!

Discoloration on a stainless steel weld is caused by atmospheric contamination. Each color indicates the temperature of the surface of the weld when the shielding gas dissipated or was removed. Excessive discoloration could be caused by overheating and could degrade its corrosion resistance and mechanical properties, making the weld rejectable; and the only solution would be to scrap the part and start over.

To prevent overheating, reduce amperage, slightly increase travel speed or shorten the arc length. Pulsing also reduces heat input, and it offers excellent control of the weld puddle. “AWS D18.2: 2009 Guide To Weld Discoloration Levels On Inside Of Austenitic Stainless Steel Tube” is an excellent guide to help determine when the level of discoloration may or may not be acceptable; you should always refer to the welding code you are using to be sure.

Sugaring (oxidation) occurs around the weld when it is exposed to oxygen in the air. The best way to prevent sugaring is to ensure you have adequate gas coverage on the front and back of the weld and to be sure that you do not overheat the weld.

Setting the amperage too high on aluminum creates a wider profile, an ill-defined bead and can potentially lead to burn-through. To solve this problem, reduce amperage and/or increase travel speed.

The color change in the middle of this aluminum weld bead can result from an increase in arc length (arc length is directly proportional to voltage). Holding too long of an arc increases overall heat input, increases the potential for distortion, widens the weld bead while decreasing penetration and affects weld bead appearance. Practice holding a consistent arc length to improve heat input control and weld bead quality.

Note: Brad Hemmert, who helped with this analysis, is a welding engineer with Miller Electric Mfg. Co.


Leave a Comment:

  • adnan wrote:

    i have continuous co2 tack-welding in my plant i need the best stick-out of feed wire
    and the best distance from face welding torch to metal , also the best angle for torch
    the quantity of co2 flow during welding
    my plant fabricate spiral pipe


  • Bob Olesky wrote:

    What causes the white oxidation on the sides of an aluminum TIG weld?

  • Andy wrote:

    The white residue is the oxide coating on the aluminum, with the right balance your cleaning action will reduce or eliminate the oxide in the weld itself.

  • Andy wrote:

    Adnan if your tig welding I would go with 2 1/2 times the electrode diameter and I would run my gas flow between 15 and 20 CFH with a pre and post purge

  • philip wrote:

    While welding Procedure qualification of dissimilar material (P1+P5A) oxidation has noticed. Gas coverage and other parameters are checked and found ok. Welding rod has changed from ER90S-G to ER80S-B3 and the issue resolved. What may be the reason of oxidation with ER90S-G?

    • Nick Peterson wrote:

      I can only speculate that your question is related to the filler metals and their chemical and physical makeup especially since this appears to be a carbon or low alloy steel. Your p-numbers only designate a group of base metals and their specific chemical and mechanical make-up could also react with the filler metal choice potentially altering the levels of oxidation but that is a deep metallurgy that is outside of my expertise. 

      A filler metal with a ‘-G’ designation is a ‘general’ filler metal designation that can have a wide range of allowable chemical and mechanical requirements when it is manufactured, hence ‘general’ in its classification number. When using a ‘general’ designation for any scope of work, one brand to the next can have significant variations between them even when they all carry the same AWS classification number. The -B3 electrode/Filler metal has more specific requirements for their chemical and mechanical make-up and variations from one brand to the next will be be significantly less. I can only assume that the -B3 electrode has more deoxidizing material in it than the –G you used, and the –B3 filler metal produced a weld that was less oxidized than the –G weld. 

      It sounds like you were able to straighten out your procedure by eliminating the general classified filler metal by going to a more specific designation. I hope that helps answer why you may have had more oxidation on your welds with the ER90S-G vs. the ER80S-B3.


  • Richard wrote:

    Bob Olesky wrote:

    >>Nov 5, 2014
    What causes the white oxidation on the sides of an aluminum TIG weld?<<

    Andy, is not the white "skirt" on each side of the weld the result of the AC cleaning cycle removing the oxide…?

  • Morgan wrote:

    Thanks for the heads up. Hindsight is always 20/20. Just got done BOMBING a weld test because some knuckle head kept the freight doors open introducing oxygen into my welds and just ruining them.

  • Jeff Blakeley wrote:

    Has been a huge help thanks for the info. Welds on Ali have gone from boiled eggs dripping off too perfect C’s :))

  • Josh wrote:

    I’m new to TIG welding. I’m doing some projects and I’m welding all kinds of metals, but cannot seem to get the hang of welding 2 mm exhaust tube (carbon steel). I just wanted to know what settings I should have on amps, gas etc.

    I have 309 filler rods 1.6 mm, pure argon gas, 1.6 mm gold electrode, size six cup, any help would be great. Thanks for your help.

    • Nick Peterson wrote:

      Hi Josh,
      Based on what you mentioned a few things come to mind. The main thing as a new welder is practice, practice, practice. It is only practice that will make you better. 
      • Gold Electrode, I am assuming is EWLa-1.5  or 1.5% Lanthanated tungsten. Gold is the American Welding Society’s designation for that type of tungsten electrode. That is a good choice. 
      • You should be welding with Direct Current Electrode Negative.
      • Sharpen your tungsten using a 30 degree Included angle.
      • Add your filler metal approximately 90 degrees to the tungsten electrode on the leading side of the weld progression (in front of the weld).
      • Use a 10 to 20 push travel angle for your electrode.
      • Use a larger gas nozzle. Many people that want to make a small weld use a small gas nozzle. A small gas nozzle restricts the area that the argon gas can shield making the completed weld essentially be shielded for a shorter time allowing more discoloration especially on stainless steel. Personally I prefer to weld with a gas lens using a number 8 nozzle or larger. If I have to reach into a tight spot, I use a much larger gas lens known as a “monster cup” and bump up my gas flow and then I can actually stick my tungsten out quite far to reach into the tight spot and the flood of Argon from the higher flow rate ensure adequate gas coverage and the thin tungsten is easier to reach in than a small gas nozzle that is minimizing how much argon is there to protect the weld and the surrounding area as long a possible allowing it to cool so that it does not become oxidized and discolor.
      • If you have the capability to pulse, pulsing can help significantly, 100 PPS 50A BKGND A 50% PEAK t is what I like, it makes it weld just a bit easier.
      • You can access a Tig weld settings calculator from Miller Here:
      • You can access a filler metal selection chart here:
      • Hopefully that helps. 
      Good luck!

  • Allan Wooldridge wrote:

    I have been trying to TIG weld steel pipe, but on some occasions there appears to be bubbles in the weld. Can you please let me know what fault this may be. Regards, Allan

  • thousif wrote:

    My cylinder hose and torch are in good condition and my travel speed is also good, but the color on each weld is getting black. I don’t want to have to buy a new machine to get good color, but I don’t know what’s happening to the machine I have now. Please give me some ideas. Thank you.

  • Julieta V. Budiongan wrote:

    I have problem on the TIG on SUS 304 as there are grounding marks as they call it or short in which the effect is the SUS 304 surface break forming circle. What is the solution for that problem?

  • Sharvan Kumar Pal wrote:

    Dear Sir: We do MIG tacking on tubular parts during welding. Some parts get effected with pin-type holes at tacking bead, and when we do leak testing of the parts, they leak from tacking. Please help me understand why this is an issue. Warm Regards. 931-153-5372

  • Cellex Okey wrote:

    Is it possible to have root undercut on weld done with GTAW+SMAW combination? Any RT picture will be helpful.



  • Ian Banks wrote:

    I am TIG welding zinc coated 2 mm mild steel and before the metal solidifies, bubbles are forming from inside the metal and lifting to the surface. Reoccurring problem, so cleaning, rewelding and it is happening again. Happens periodically, on some welds not all. I am using Argon gas and TIG welding mild steel rods. Any suggestions for a solution, please?

  • Danilo Latcharon wrote:

    We have a weld mark problem for aluminum. After Black hard anodizing the weld mark is very visible at the other side. How can we prevent that?

  • David Curry wrote:

    I recently bought a Miller Diversion 180 TIG welder. When I hooked up the argon tank and adjusted the flow, the gas automatically started flowing through the torch tip without the pedal depressed. Is that normal? Any help would be appreciated. Thanks, D.Curry.

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