Common Welding Problems and How to Fix Them.

Welding isn’t just as easy and making sparks and melting metal together. A good weld requires a lot of skill and can take years of practice to get perfect welds consistently. If you’re having problems undercutting, excess weld spatter, or porosity in a weld you may need to diagnose your weld settings and technique to correct the issues. Below we discuss these issues and ways to correct them.


Undercutting of a weld is easy to spot and happens to the best welders from time to time. A undercut weld or weld undercutting is when there is a groove or recess next to a weld where some of the surrounding metal falls into the weld seam and you’re left with a groove and sometimes jagged edge next to the weld seam. This can be a failure point for structural welds and can also be a visual issue if the edge of a weld seam needs to be unharmed after welding.

Causes for an Undercut Weld

  1. Travel Speed- If your travel speed is too quick you can find that you will get undercutting of a weld because the metal is solidifying to quickly causing a weld that has peaks in it or are sitting high above the weld seam. Too fast of a travel speed will draw the surrounding metal into the weld seam and the filler material cant “wet” out into the seam and flatten. Try adjusting your travel speed to see if you get a flatter weld with less undercutting.
  2. Torch Angle- Incorrect torch angle can be an issue especially when welding dissimilar thickness materials together. If your torch angle is putting more heat on the thinner material you will get a pronounced undercut on that side of the weld seam. This can also occur on material the same size if the weld seam is a lap weld were the top material has gravity pulling it down as well when welding. Try adjusting your torch angle when welding to avoid this problem.
  3. Welder Settings- If you don’t have your welder set correctly and you have the welder set too high for the weld joint or if your ratio of filler material to welder heat/power settings isn’t correct the weld will get too hot and start pulling material from the edges of the parent material into the weld seam causing undercutting. This can be a matter of lowering the welding amperage or voltage or adding more filler material to the weld. This sometimes comes down to personal preference, but the suggested settings that come with your welder should be a good starting point.

Causes for Excessive Weld Spatter

  1. Dirty Metal/ Weld Contaminants- Your weld surface should be as clean as possible and any oil, grease, rust, or coating can cause excess weld spatter and a contaminated weld. Make sure that you’re mechanically removing any surface corrosion or coatings first and then following up with a solvent like Low VOC PRE or Acetone to clean greases or oils off of the surface before welding. This will greatly reduce the weld spatter and give you a nicer finish to your weld.
  2. Incorrect Weld Setting- If you’re using a MIG welder you could have an issue where you have your wire speed set too high and the welding wire is bouncing off of the panel and creating a lot more spatter than actually melting into the weld seam. Try adjusting your wire speed down or heat up to get less spatter and a flatter weld.
  3. Shielding Gas- If you’re using a welder that requires shielding gas you need to have adequate gas flowing over the weld puddle to keep contaminants out of the weld puddle during the welding process. Make sure you don’t have any restrictions at the torch and you can hear/feel the gas coming out of the nozzle when you hit the pedal or trigger. Also check to make sure your bottle isn’t low or out of gas.

Causes for Weld Porosity

  1. Welding Technique- Welding technique can actually cause porosity in a weld puddle. If you’re moving too quickly or your welding torch is too far from the weld puddle the shielding gas may not get to the weld seam and the weld can get contaminated and cause porosity. This can be solved by making sure you’re moving at a steady rate of speed and you have the proper distance from the surface so the shielding gas can do it’s thing and protect the weld.
  2. Shielding Gas- Make sure you have enough gas flowing out of the torch and it isn’t be blocked by weld spatter in the nozzle. Also make sure your gas bottle isn’t empty. The last thing is to make sure that you have the correct welding gas for the material and type of welder you’re using. For instance Aluminum welding requires 100% Argon even when welding with a MIG welder and TIG welding requires 100% Argon even when welding mild steel. So check that you have the correct type of shielding gas for what you’re welding.
  3. Dirty Metal- If the metal has coatings, rust, or oil on the surface it will be heated up when you weld and get into the weld causing popping and porosity.

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