Top 5 bad welds – how to spot them

Updated: Jun 15


By Ed West, Custom Welder Team Lead


See how to spot a bad weld when reviewing your next project for quality

With 30+ years of experience and having gone through training to receive the American Welding Society (AWS) Welder Certification in the past, I recently moved into managing our welding team at the Lexington site.

I ensure that I do continuous training with the team on metal inert gas (MIG) welding, which is often used when speed is required. I also do quite a bit of tungsten inert gas (TIG) welding, which takes longer but man, does it look better and hold well for complex projects.


I see welding as an art form; and everyone I hire thinks so too.

Sometimes customers will come to us to fix metal pieces after a safety issue has come to the surface. I always want customers to know proactively how to spot a bad weld rather than waiting for something to happen.


1. Porosity


With porosity, the welder’s mistake is not enough gas used or wind overhead hitting the metal. It creates a poor cosmetic finish and weakens durability because the material hasn’t fully bonded.


2. Undercutting


The weld is too hot so it actually cuts into the metal weakening the material, itself. This creates structural integrity issues and cracks. While I won’t get into the nitty gritty, the fabricator details how far is too far.


3. Cold weld


Cold welding happens when the weld voltage isn’t set to the right temperature, and the weld is laid on top of the metal. It won’t hold with the incomplete fusion. This will be very obvious with inspection.


4. End Craters/Cracks


End craters and crack occur when the welder stops too early, especially at the corners. The welder should be wrapping the weld and go from the two opposite sides to meet them. (S)he should overlay slightly with the last beads. You are going to see structural issues over time if you don’t do this right, but it may not be immediately.


5. Spatter


You can see the little balls of metal all over the place. Cosmetically, It does not look good and shows lack of pride in the work piece.


These ruin the cosmetic finish of your piece. It’s like seeing a beautiful face with pimples all over it.

It can also throw off the measurements of the rest of the project, especially if it’s part of the base. I always start by using my scraper.



Then, I used my flat disk to finish cleaning it off for a smooth surface.