Welding Gas – What Types to Avoid & Use

Last Updated on Nov 19, 2022

Welding things takes more than just heating two metal objects to join them together. It requires a lot of knowledge about the different welding techniques, the different types of welding equipment, and the different gasses that one might use for welding.

If you didn’t know already, welding is done through the use of several different gasses- each with its own set of unique properties that make them the best gas for certain types of welding. Experienced welders have a good handle on this; they know what gas would work best for a certain welding situation.

If you’re new to welding, all of this can seem pretty complicated, and to be frank, it is. But don’t worry- we’re here to help. Stick with us, and we will teach you about the different types of gasses used in welding and their unique purposes.

Inert vs. Reactive Gas

Let’s begin by understanding the two main classifications of gasses used in welding. These classes are namely inert gasses and reactive gasses.

Inert Gasses

Inert gasses are gasses that remain unreactive under special conditions. These gasses include noble gasses as well as some compound gasses. It is important to note that being an inert gas does not mean that these gasses remain non-reactive no matter what.

As an experienced welder will tell you, inert gasses can be made to react strongly if their surrounding conditions are tweaked a certain way. This is why many emphases are laid upon learning about the properties of the different types of gasses used in welding.

Reactive Gasses

These gasses chemically combine with the constituent substances in the weld pool to alter the properties of the metals in the welding mix. These gasses can easily change the nature of the welding mix, so all welders must know when and how to use these gasses to bring about the desired effects. Some common examples of reactive gasses include nitrogen, hydrogen, CO2, and Oxygen.

We often mix inert gases with a mix of reactive gases of low concentrations during welding. The inert gases help stabilize, thereby protecting your weld by preventing the metals from undergoing undesirable chemical reactions.

On the flip side, the reactive gases will make alterations to the mix, such as increasing the temperature or altering the composition of the filler metals. This is why it is crucial to be aware of the difference between inert and reactive gasses and their correct usage.

Choosing the Right Gas for You

Typically, Gases serve four main functions in the process of welding. These are, namely:

  1. Shielding
  2. Purging
  3. Heating
  4. Blanketing

We examine each of these primary functions in the lines that follow.

Shielding Gas

Shielding gases, as one can tell from their name, shields the weld from any air that might enter the arc and result in the formation of air pockets in the molten mix of metal. This results in a weak and unsightly weld. When MIG or TIG welding , shielding gas must be used unless your filling material is “flux-coated.”

Shielding gases are typically inert- they will not react throughout the welding procedure and hence will not affect the weld’s integrity or structure.

The inert gas you choose has an effect on how the weld performs and may increase penetration, alter the metal’s fluidity during melting, and provide a flat surface on the bead.


Purging gases perform a function that is similar to shielding gases, except this is more towards the underside of the welding mix. Purging is mainly utilized during the welding of stainless steel, and it is performed by closing off the bottom side of the joint and passing the purging gas on it.

Heating Gas

There are other types of welding, including gas welding or brazing, which utilize the gas flowing in the gun to boost the temperature of the filler rod response. Naturally, this needs a reactive gas. Also, note that when a gas is used to generate heat, arcs are not needed.

Blanketing Gas

Blanketing is relatively uncommon, but it is used to guarantee that a weld is not tainted or polluted once it is completed. Gas is injected into the area surrounding the weld to push away any airborne impurities.

This may be accomplished by putting the completed object in a gas tank or by pushing gas out from the current area and putting in an inert gas there in place of it.

Types of Welding Gas

Now, let’s take a look at some of the most commonly used gases in welding, their important properties as well as their correct use.


We’re all pretty familiar with this one. Oxygen is a gas that is crucial to the survival of all living beings on Earth. So, it’s only natural that so many people know about it. What you may not know about Oxygen, though, is that it is one of the key gases used for welding. Oxygen has no taste, no smell, and is extremely reactive.

When Oxygen is used in welding, it is often combined with different shielding gases to alter metal’s fluidity and catalyze the process.

Additionally, you may use it to increase the temperature during welding. Specifically, when Oxygen is combined with acetylene, it produces a flame powerful enough to forge steel (This is the only type of flame that can achieve this).

Lastly, Oxygen also helps eliminate the necessity for a “shielding flux filler wire” from the welding process.

Carbon Dioxide for Welding

Carbon Dioxide is also commonly referred to as MIG gas. You might better know this gas as the one which all living creatures exhale, but did you know that this gas is pretty popular in the ambit of welding as well?

Carbon Dioxide is another naturally found gas which is commonly used for welding. This one is relatively inexpensive and easy to manufacture on large scales, and it is the most commonly used gas in MIG welding. One of the key functions of Carbon Dioxide in welding is shielding the arc as well as the molten pool.

CO2 is even less costly than Argon; however, it has a noticeable impact on the weld quality in comparison to Argon, and it may also produce more spatter than Argon. As a result, Carbon Dioxide is often mixed with other substances during welding instead of being used in its pure form. One commonly used blend of Carbon Dioxide is achieved when the gas is mixed with Argon.


Member of the inert classification of welding gases, Argon gas, is used in a variety of welding operations. Argon does not react to a vast majority of other chemicals (except at incredibly high temperatures). As the third most prevalent gas on the planet, it is also a relatively economical alternative to utilize for welding.

It is a shielding gas that is often utilized when dealing with stainless steel, aluminum, or titanium, but it may also be used with regular carbon steel since it significantly improves the stability of the arc and the flow of metal from the electrode towards the weld pool.

It may be utilized during the main welding cycle or to purge the joint’s underbelly. It’s a safe bet for MIG welding as well as the industry standard for TIG welding. Argon cylinders are an indispensable need in most welding sites since argon gas is most commonly used for shielding, specifically to keep impurities out of the air.


Helium is remarkable welding gas in that it does not freeze – it may exist in a liquid form but never in a solid one. Additionally, it makes you speak strangely if you breathe it in, which is how the majority of us come into contact with it.

Helium is scarce on Earth and difficult to create, making it relatively costly in comparison to other welding gases. It is employed as a shielding material both alone and in blends because it aids in intense penetration and increases heat input; however, it may be difficult to start an arc with it.

Helium is most effective, though, when combined with Argon, which adjusts for Helium’s uneven beginning qualities. This kind of mix is often employed for the welding of nickel alloys.

The practice of welding is far more complex than most people think it is and a crucial part of becoming an experienced welder is to know about the different classifications and types of welding gases that are used.

In addition to knowing which gases are used in welding, one must also be aware of which classification of gasses they fall under, i.e., whether the gas is inert or reactive.

Inert gases are relatively non-reactive (except under special conditions) and are used in welding to stabilize the process. Reactive gasses, on the other hand, alter the nature of the welding mix and are used in combination with inert gases to produce the desired effect.

Welding gasses serve four primary purposes, namely:

  • Shielding,
  • Purging,
  • Blanketing

It would be best if you chose gases for welding according to the purpose you want them to serve in your welding procedure.

Lastly, Oxygen, CO2, Argon, and Helium are all examples of some of the most popular gases used in welding – and each gas has its own unique set of properties and purpose in welding.