Understand Porosity When MIG Welding for Optimal Results

Welding is an art form, but it is also a highly technical skill. It is not something you can just pick up and do correctly without learning the basics. This is particularly true of MIG (Metal Inert Gas) welding, which is one of the most common types of welding. Every welder should understand the basics of porosity when MIG welding and how to minimize it for the best results.

What is Porosity?

Porosity is a key issue when it comes to welding and is one of the most common welding defects. Porosity is the presence of small gas pockets in the weld joint that are formed when the molten metal solidifies. These pockets can weaken the weld joint, making it susceptible to cracking and other issues.

What Causes Porosity When MIG Welding?

There are several factors that can lead to porosity when MIG welding. The most common are:

  • Contamination: Contamination of the weld joint can lead to porosity. This can be caused by dirt, oil, grease, or rust. It is important to ensure that the weld joint is free of any contaminants before welding.
  • Incorrect Welding Technique: An incorrect welding technique can also lead to porosity. This can include improper travel speed, incorrect angles, and incorrect electrical settings.
  • Poor Shielding Gas Quality: Poor quality shielding gas can also lead to porosity. The shielding gas should be clean and free of any impurities.
  • Improper Joint Preparation: If the joint is not properly prepared, it can lead to porosity. This includes ensuring that the gap between the two pieces of metal is not too large or too small.

How to Minimize Porosity When MIG Welding

There are several steps you can take to minimize porosity when MIG welding. These include:

  • Ensure that the weld joint is free of any contaminants before welding.
  • Use the correct welding technique, including the proper travel speed, angles, and electrical settings.
  • Use a high-quality shielding gas that is free of any impurities.
  • Ensure that the gap between the two pieces of metal is correct.
  • Use the correct welding wire for the job.
  • Keep the welding gun at the correct angle.
  • Move the welding gun in a consistent manner.
  • Keep the arc length constant.
  • Use the correct welding technique for the job.
  • Ensure that the welding current is correct.


Porosity is a common problem when it comes to welding, but it is also something that can be avoided if you take the necessary steps. By following the tips outlined above, you can minimize porosity when MIG welding for better results. With practice and a good understanding of the basics, you can become a master welder.

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