What Causes Porosity in MIG Welding? (Proven Ways to Fix it)

There are four main welding methods: metal inert gas (MIG), tungsten inert gas (TIG), stick, and flux-corded welding. The common method is MIG, whose patent was in 1949 in the USA.

Even though it has been in existence for a while, there are some factors that you need to know about metal inert gas welding. The main point you should know is what causes porosity in MIG welding.

You might be wondering why porosity is occurring on the joined parts after welding. Contaminants are what lead to such a situation.

So, today you will learn about causes, ways to fix, and how to prevent porosity in MIG welding.

Porosity in MIG Welding

What is MIG or Metal Inert Gas Welding?

This arc welding type involves continuous heating of a solid wire electrode to a weld pool using a welding gun. The welding gun generates a shielding gas together with the electrode.

The shielding gas is vital in preventing any air contaminants from entering the weld pool.

This is crazy: If the welding gun produces a shielding gas, how do contaminants enter the weld pool, causing porosity?

To know more about that, continue reading.

What Causes Porosity in MIG Welding?

Knowing how to weld doesn’t guarantee you that when using this welding method, you won’t cause porosity. You require to have experience and have done thorough practice.

Before you start the welding process, it is best to check your equipment. Additionally, check your speed as it is vital as you weld.

Various factors lead to porosity in metal inert gas welding. They include;

• Varying Gas Flow

The required gas flow is ideal in welding and helps in preventing porosity in welding. But if the gas flow is either high or low, there are high chances of porosity.

Be careful of your gas flow as various things lead to high or low gas flow. Moisture and leakage are the most common issues.

The ideal gas flow rate for MIG welding is 20 to 25 cubic feet per hour.

• Empty Gas Cylinder

When the gas cylinder is empty, it has a high chance of leading to porosity during metal inert gas welding. That’s why it is vital to check your gas cylinder each time before welding.

This helps you to know the amount of gas remaining.

• Air Drafts

Suppose you leave your door or windows open. Or you don’t keep the welding gun or weld nozzle at the right distance from the welding material.

Such can lead to the formation of air drafts. Thus, requiring you to redo the work again. This is stressful and annoying.

When welding, ensure you keep the right distance between the welding material and the gun. Also, close your windows and door always.

• Dirty Tools

Your welding tools need to be clean before a welding process. Some of the things that make your equipment dirty are oil, dust, powder, and rust.

They may seem small but are a huge factor when it comes to metal inert gas welding. When such dirt mixes with your weld pool, it contaminates the materials. Thus, causing porosity.

Note: Always clean your welding tools after each welding process.

• The Nozzle Distance and Welding Gun Angle

Experts recommend that the suitable nozzle distance is a maximum of a half-inch from the welding material. When it is more than that, there is a high possibility of porosity.

Additionally, as a welding operator, the gun’s angle should be 90-degrees. Suppose the angle is more than the recommended you will experience porosity after welding.

• Excessive Use of Gels, Anti Spatter Compounds, or Sprays

The use of anti-spatter compounds in welding is common. This is because these anti-spatter compounds prevent spatter from clogging on the welding gun nozzle. When you use too much of it leads to contamination as you weld.

Additionally, the spray and gels will act the same. Thus, when welding, they will boil and spill, causing contamination.

• Defective Hose

A hose is defective when the hose is either cut or is burnt. This can lead to contamination. So, it is vital to check the hose every time before welding.

It is essential in preventing the occurrence of porosity.

How Do You Fix Porosity on a MIG Welder?

Porosity in metals happens for various reasons, but the most common is unclean welding material surface and varying gas flow.

To fix porosity in welds, you must know what issue has led to porosity during the MIG welding process. 

You must ask yourself what contaminant has brought about porosity in your weld.

Get to discover if they are the following issues.

  • Unclean surface
  • Clogging due to spatter
  • The gas flow rate
  • Due to rusting

When you discover the problem, you can comfortably tackle the contamination and continue with your welding process.

Before you begin welding, make sure your surface is clean and the gas flow is average.

Reasons Why MIG Welding is the Best

Why do many welders and companies prefer metal inert gas welding to other types of arc welding? There are various reasons for this.

Below are the reasons to use MIG welding.

• Easy to Learn

Many welders prefer this type of arc welding because it takes a short time to learn and master. This makes it simple for a beginner to weld like an expert.

Unlike tungsten inert gas welding, which requires you to be an expert. MIG requires you to weld using a hand.

• Cost-Effective

Every manufacturing company is after profits, and their production rate determines that. TIG takes time, meaning it will cost you more.

But when you go for MIG, it is cost-effective. This is because it takes a short time to weld, meaning you can complete a huge project faster.

• Diverse

Although the welding method you choose is compatible with all types of metals, its effectiveness boils down to efficiency. Metal inert gas welding works well on metals.

Meaning you can use it on the metal of your choice while the efficiency will remain the same. This is regardless of the thickness of the metal.


MIG welding is the common arc welding method, but porosity tends to be a huge issue with many welders. We hope this guide has enabled you as a welder to learn more about porosity in metal inert gas welding.