The Difference Between Gas and Flux Core MIG Welding

Gas MIG welding versus Gasless MIG welding - what exactly is the difference? The truth of the matter is this: the term “gasless” MIG welding is actually a bit of a misnomer. We say this because every form of welding currently in use today relies on some kind of gas.

In the art of welding, the gases - known as shielding gases - are required to protect the welding area from commonly found gases in the atmosphere, such as nitrogen and oxygen, which can spoil the weld. If these atmospheric gases come into contact with the welding metal, arc, or electrode, they can cause defects in the fusion as well as porosity and weld metal brittleness.

This problem is actually common to all welding processes.

So if all welding processes rely on some type of shielding gas to protect the weld area, what is meant by the term Gasless MIG welding? And what are the major differences between Gas and Gasless MIG Welding? These are the questions we will answer below in some detail.

What Do the Terms Gas MIG Welding and Gasless MIG Welding Actually Mean?

Under the broad category of welding known as “Arc Welding,” there are welding processes that are familiarly referred to as Gas Welding and Gasless Welding. Below we will briefly define each of these terms:

Gas MIG Welding Defined

Gas MIG welding, also known as Gas metal arc welding (GMAW) or simply MIG Welding - Metal Inert Gas Welding - is a welding process in which an electric arc forms between a consumable wire electrode and the work-piece metal. This arc heats the work-piece to a high degree, ultimately causing the two pieces to melt and coalesce - or join together.

In addition to the wire electrode, a tanked shielding gas is fed through the welding gun - a gas that shields the welding area from contaminants in the air. This process can be automatic - in which the shielding gas is constantly fed - or semi-automatic, in which the shielding gas is activated by a separate switch.

In Gas MIG welding, a constant voltage, direct current power source is mostly used, but some torches can also run on direct current (battery power) as well.

Gasless MIG Welding Defined

Gasless MIG Welding, also known as flux core welding, is another popular form of welding, largely because it is cheaper and very easy to learn. Like with Gas MIG welding, in Gasless MIG welding a consumable electrode is used, but in this case the flux is inside the wire electrode.

Also just like Gas MIG Welding, in Gasless MIG welding an electric current, in the form of either alternating current or direct current from a welding power supply, is used to form an electric arc between the electrode and the two (or more) metals to be joined. The work-piece and the electrode melt forming a pool of molten metal (weld pool) that ultimately cools to form a joint. As the weld is laid, the flux interior of the electrode disintegrates, giving off vapors that serve as a shielding gas and providing a layer of slag, both of which protect the weld area from atmospheric contamination.

Gas MIG Welding versus Gasless MIG Welding: Shielding Gas Explained

As we mentioned in the introduction, in the processes known as Gas MIG Welding and Gasless MIG Welding, both rely on a shielding gas to create a perfect or near-perfect weld. So why is one of the processes called Gas MIG Welding while the other is called Gasless MIG Welding? The answer to that is rather simple.

In Gas MIG Welding, a gas source is actually connected to the torch mechanism. When the arc is created, the gas is released from the tank and through the torch to protect the area from atmospheric contaminants.

In Gasless MIG Welding, the electrode that is used to lay the weld contains a flux material. When this flux material is heated, it emits a protective halo of flux around the work area to protect it from the same type of atmospheric contaminants. In other words, instead of relying on a tanked gas, flux core MIG welding relies on a flux material to produce the needed shield.


The types of shielding gas used/produced for each type of welding process (Gas vs. Gasless) also tend to vary. In gas metal arc welding, the type of gas used to protect the weld area from contaminants usually varies depending on the job. For nonferrous metals, for example, inert gas such as argon is typically the most popular choice.

Some welders even use a combination of helium and argon. In jobs involving steel, however, the inert gases such as helium and argon do not provide sufficient penetration into the weld, or they can cause an inconsistent arc and encourage molten spatter. Pure carbon dioxide is an option for steel, as it allows for deep penetration welds, but this gas also encourages oxide formation, which adversely affects the metallurgical properties of the weld.

The low cost of CO2 makes it an attractive option as a shielding gas, but because of the unpredictability of the arc, spatter is unavoidable and welding thin materials is difficult. As a result, argon and carbon dioxide are frequently mixed - usually in a 75%/25% to 90%/10% mixture - for jobs involving steel.

In the process known as Gasless MIG welding, the flux in the electrode, when heated, provides a protective cloud of carbon dioxide that can be used for almost any type of welding jobs. However, there are some drawbacks to this type of welding. The flux that is used to produce the carbon dioxide shielding gas tends to build up after welding in the form of slag or impurities. This must then be chipped off to reveal the completed weld.

Gas MIG Welding or Gasless MIG Welding: Which Is Right for You?

Now that you understand the basic differences (and similarities) when it comes to both Gas MIG welding and Gasless MIG welding, which process should you use to get the job done? This will actually rely on plenty of factors, including your level of skill, the type of metals to be welded, your budget, etc. To help you make an educated decision, below we have listed some of the things you should know about each type of process, including the benefits and disadvantages associated with each.

Gas MIG Welding: What You Should Know

Gas MIG Welding is a fairly easy process to learn.
Once you learn how to program and set the parameters of the welding torch, and become proficient in choosing the right type of shielding gas for different types of jobs, the rest is actually pretty easy.

In GAS MIG welding, a tool known as a spool gun is used to feed the wire electrode at a constant speed - a speed predetermined by the welder. This electrode - and the work-piece - are then melted by the arc, as the shielding gas is emitted to protect the weld area from contaminants. This process forms a weld pool that, when cooled, will form a strong joint.

Benefits of Gas Mig Welding

There are many benefits to choosing the Gas MIG welding process, including:

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    High strength welds. The welds from GAS MIG welding are known to be very strong and can stand the test of time.
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    Clean, neat welds. Gas MIG welding creates little or no slag that would normally have to be chipped or sanded, meaning less cleanup time for the operator.
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    Continuous Welding. The use of the shielding gas and the automatic electrode feeder allows the welder to operate at a continuous rate, making the welding process much more efficient.

Drawbacks of Gas Mig Welding

  • Expensive. The cost of buying or renting tanks full of shielding gas can quickly get expensive when using the Gas MIG welding process.
  • Hard to use outdoors. Because the shielding gas has a tendency to blow around in the wind, this process is not recommended for outdoor welding, making it very limited in scope.
  • Must master the machine. When using a gas MIG welder, the operator must be proficient at setting the parameters, which can be difficult to learn.

Flux Core MIG Welding: What You Should Know

During gasless MIG welding, an electrode that contains a flux core, along with the power supply to create the arc, is used to lay the weld. During the process, both the electrode and the metal work-piece melt, forming a weld pool. This molten pool then cools to form a sturdy joint between the two metals.

Benefits of Flux Core Mig Welding

There are some pretty good arguments to be made for turning to flux core MIG welding, including:

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    Affordable. Although the flux containing wire electrode can cost a bit more than the regular electrode used in Gas MIG welding, there is no shielding gas to buy, which makes the process much more affordable.
  • there is no shielding gas to buy, which makes the process much more affordable.
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    Versatile. Gasless MIG welding can be used with many different types of metals, including steel, iron, aluminum, nickel and even copper.
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    Can be used anywhere. Unlike gas MIG welding, which is not recommended for outdoor use, Stick welding can be performed anywhere.

Drawbacks of Flux Core Mig Welding

  • Irregular welds. Welds using the Gas MIG welding process are usually clean, requiring no cleanup, chipping or sanding. Not true with Flux Core Welding, which produces slag that must be cleaned off to expose the weld joint.
  • Time-consuming. Compared to Gas MIG welding, Gasless MIG welding is very time consuming. Much time is spent changing out electrodes and the sanding and chipping that must be done after the job can be very labor intensive.

As you can see, there are arguments to be made both for and against each type of welding. For beginners, we recommend you learn your trade using the Gas MIG welding process, as it is much easier to learn and much more affordable. As you become more proficient, you can always work your way up to stick welding. If you can get your hands on a machine such as the Rebel EMP 215ic, you will be able to undertake multiple types of welding processes, as this is a machine with great functionality and can execute many different welding tasks.