Welding Porosity: What It is, Causes and How To Avoid

Marcus Colson Last updated on September 4, 2023
Reading Time: 4 Minute

Welding porosity is a common issue that a welder encounters in welding processes.

It involves the formation of small, spherical cavities or holes in the welded joint.

In addition, porosity in a weld can weaken its integrity and cause failure.

Thus, it leads to expensive repairs or replacements.

Learn about what porosity in welding is, its causes, and how to prevent it here.

What is Welding Porosity?

Porosity in welding is the presence of small cavities or holes in a welded joint.

The common cause is the entrapment of gas bubbles during the welding process.

In addition, gas bubbles are a result of various factors.

There are broken shielding gas, contaminated base metal or filler metal, or wrong welding techniques.

Porosity can manifest in different forms.

The forms can be surface porosity or internal porosity. A welder can detect it through visual inspection or non-destructive testing methods

Moreover, surface porosity appears as small, more visible holes on the surface of the weld.

At the same time, the internal porosity is invisible to the naked eye. Thus it can only be detected through X-ray or ultrasonic testing.

Read Also : Inductance in Welding: Don’t Let It Ruin Your Welds

Causes of Welding Porosity

There are several causes that lead to porosity in welding.

Here is the list of the welding porosity causes.

Improper Shielding Gas

Shielding gas plays an important role in protecting the weld pool from atmospheric gases such as oxygen and nitrogen.

In addition, those gases are the ones that can cause porosity. 

The most common shielding gases for welding are argon, helium, and carbon dioxide.

Hence, if the shielding gas flow rate is too low, or the gas mixture is not appropriate for the welding process, porosity can occur.

Contaminated Base or Filler Metal 

Contamination of the base metal or filler metal can also cause porosity.

Examples of contaminants are rust, oil, grease, or moisture.

In addition, they can release gases when exposed to high temperatures during welding, leading to porosity.

Therefore, cleaning and preparing the base metal and filler metal thoroughly before welding is important to avoid contamination.

Once it is clean, the chance of getting porosity is lower, and the metal welding process will be smoother.

Hence, the result of the welding has a good bead and looks smoother.

Improper Welding Technique

The welding technique used can also contribute to porosity.

If the welding technique is unsuitable for the type of joint being welded, it can lead to porosity.

Also, if a welder uses a too-fast welding speed, it will only worsen the condition.

In addition, porosity can also occur if the welder does not maintain a consistent distance between the electrode and the workpiece or if the electrode is contaminated.

Porosity in a metal can occur due to some of the factors above.

However, some are preventable if the welder thoroughly prepares beforehand.

Doing so can lessen the probability of getting porosity or imperfect welding result.

Below are some ways to prevent porosity during or after the welding process.

How to Prevent Welding Porosity

Here is how to prevent porosity during welding. Some of the ways below are something welders need to take care of.

The list below shows how to prevent porosity before and during welding.

Proper Shielding Gas

To prevent porosity caused by an improper shielding gas, a welder ensures that the gas flow rate and mixture are appropriate for the welding process. 

Also, the gas flow will need proper adjustment to meet the type of the workpiece.

In order to suit the welding conditions, the welder should mix the perfect ratio for both the gas and the type of welded metal.

Furthermore, a welder should prepare the shielding gas beforehand to ensure the process does not get bothered.

Hence, such porosity is something preventable.

Clean and Prepare Base Metal and Filler Metal

In order to prevent porosity caused by contaminated base metal or filler metal, it is important to clean and prepare them thoroughly before welding.

Cleaning the base will remove any materials that will only disrupt the welding process.

Moreover, those materials can also make the welded object not look as smooth.

Clean the metal base first by removing any rust, oil, grease, or moisture from the surface of the metal. A welder may use a wire brush or chemical cleaner to clean the metal base.

Use The Right Welding Technique

Using the right welding technique can prevent porosity.

Ensure that the welding technique is appropriate for the type of joint being welded and that the welding speed is not too fast.

Maintain a consistent distance between the electrode and the workpiece, and ensure that the electrode is clean and not contaminated.

Check Welding Equipment and Materials

Another way to prevent metal porosity is by checking the welding equipment.

Also, preparing the material beforehand is essential to guarantee a smooth welding process.

Check the welding equipment and materials regularly to ensure they are in good working condition. 

Another case of porosity can also occur because the machine and the materials are both worn-out and getting used too frequently.

If so, replace any worn-out or damaged equipment and materials to prevent porosity.

Buy a new one or make sure to have the stocks stacked up before the machine and the materials are worn out.

Monitor Welding Environment

Even though all the materials and the machine are not the problems, one obstacle still unknowingly causes porosity. It is the environment where the welder welds the metal.

The welding environment can also contribute to porosity.

Hence, a welder must ensure the welding area is free of drafts and other atmospheric gases. 

If there are some corrosive materials in the workplace, it is likely to cause porosity. Use a welding curtain or shield to protect the welding area from air currents if necessary.

Read Also : Understanding Welding Parameters: Your Key to Perfect Welds

In conclusion, welding porosity is a common issue during the welding process.

The causes are actually preventable. A welder can take precautions before starting the welding. 

Moreover, the environment where the welder works on the workpiece is also essential.

Make sure to take notes of the causes listed above to prevent porosity.

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Marcus Colson
Marcus Colson

Welding is more than a hobby for me - it's a passion. The art of fusing metal together to create something new and functional never gets old. From intricate sculptures to sturdy structures, I love the endless possibilities that welding offers.

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