Battle Of Flux Core Welding VS Mig Welding :(FCAW VS GMAW)

Flux Core Welding VS Mig Welding

No matter how long you have been welding, the terms flux core welding and MIG are two you have come across. These are arguably the most common welding processes on the planet. But which method is the better of the two?

Well, the truth is no one welding process is better than the other. Each welding process has its pros and cons. Therefore, it all depends on several things. However, this doesn’t mean we cannot compare the two welding processes.

In the battle of flux core welding vs mig, there are several things we need to look key, among them the main similarities and differences.

Introduction to flux core arc welding

What is flux core arc welding?

Flux core arc welding dates back to the 1950s. However, technically speaking this wasn’t a new process. Instead, it was more of a new kind of electrode that could be used on MIG welders. In this regard, there are a lot of similarities between these two processes.

In flux core welding, the electrode used contains flux materials in its core. These materials create a shielding gas when burned. Therefore, unlike in Metal Inert Gas welding, there is no need for an external gas container to supply shielding gas.

flux core welding

Flux core welding applications

The main benefit of flux core welding is that it can be done outside in windy conditions. As such, it is ideal for outdoor welding applications. This can include farm work, auto body repair works, and general welding projects.

Also, flux core welding is used in ship building as well as welding of pipes. Manufacturing and underwater welding are the other two main applications of FCAW.

Advantages of flux core welding over mig

  • Unlike MIG welding flux core welding can be done outside in windy conditions
  • Flux core welding unlike MIG welding can be used on dirty or rusted metals
  • Since there is no need for a gas tank as with MIG welding it is more portable and cheaper
  • Unlike MIG welding flux core welding can be done in vertical and overhead positions.

Disadvantages of flux core welding

  • Produces high levels of noxious fumes and thus ventilation is required
  • Flux core wires are relatively costlier than MIG solid wire
  • Produces slag that has to be removed after welding

Introduction to Metal Inert Gas welding

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What is MIG welding?

As you probably have already guessed Metal Inert Gas welding is the older of the two. In this technique, a consumable wire electrode is used to make an arc between the metal and electrode. While doing so, heat is produced, and shielding gas is supplied from an external container.

Thus unlike in flux core welding, you need an external gas container for MIG welding. The electrode used here does not have any flux materials.

mig welding process

MIG welding applications

MIG welding has almost the same applications. But unlike flux core welding, MIG welding is used for welding both ferrous and non-ferrous metals. Therefore, it is used in shipbuilding, automotive industry, and in the production of pressure vessels.

Steel structures are also welded using this method. Additionally, since it can weld aluminum, it is used in making aluminum products.

Advantages of MIG welding over flux core

  • Unlike flux core welding MIG welding produces aesthetically pleasing welds
  • The slag produced from MIG welding is easier to remove compared to that of flux core welding
  • MIG welding can be used on both ferrous and non-ferrous metals unlike flux core welding that is used only on ferrous metals.
  • Due to the use of a gas tank supplied shielding gas there is little alloying element lost and minimal spatter compared to flux core.
  • Compared to flux core welding and other welding processes is relatively easy to learn

Disadvantages of MIG welding

  • Can only be used on clean metal surfaces and cannot work on dirty, rusted or painted surfaces
  • Less portable due to the need for an external gas tank
  • Cannot be done outside.

FCAW and GMAW principle

The principles behind these two welding processes are primarily the same. In both, a wire electrode is fed onto the base metal to form a welding arc. Current from a power source passes through the electrode and causes the arc to heat up. As a result, the metal of the metal creating a weld joint.

Due to the heat generated, the weld pool can react with the oxygen in the atmosphere. This causes the pool to oxidize, which results in a poor weld. To avoid, this a shielding gas is supplied, which shields the weld pool from external contaminants and oxygen in the air.

In MIG welding, the shielding gas is supplied from an external gas container. In Flux core welding, the shielding gas is generated from the burning of the flux material.

Equipment used in MIG and FCAW

When you’re deciding between flux core vs mig then one thing you will want to know is which machine to use. These two processes use mainly the same welding machines. The only difference is in the type of electrode used.

You can use a standard MIG welder for FCAW welding. The only difference is that you will not require an external gas container. When you decide to opt for MIG welding, you will need to purchase an external gas container.

Some welding machines come with this container already included. However, some do not.

Flux core welding vs mig welding: other considerations on which to choose

Flux Core Welding VS Mig Welding

Which wire/electrode to use?

As mentioned above the main difference between the two is the electrode used. In MIG welding, a solid wire electrode is used. Purchased in the form of a spool welding wire, the wire isn’t hollow.

In flux core welding, the welding wire used is hollow. On the outside it’s made of metal; inside, it contains a flux material. It is this flux material that is the source of its name.

The shielding gas used

Many who are on the side of flux core welding in the battle of flux core welding vs mig, prefer it due to its portability. When it comes to MIG, there is a need for a pressure gas tank connected to a regulator or flow meter.

A hose runs into the MIG welder and feeds the gas from the pressure tank to the welder. Self-shielded flux core wire produces its own protective gas. However, there is a type of wire, the dual shielded flux core wire that requires an external gas.

In MIG, several gases are used to provide protection. They include carbon dioxide, argon, a mixture of argon and carbon dioxide. For stainless steel, a mixture of helium, argon, and carbon dioxide gases is used.

For gas-shielded and dual shielded flux core wire, the same gases are used.

How much spatter and slag is produced

In the mig vs. flux core welding, some side with MIG because it produces easy to clean slag. Due to the flux contained within a flux core wire, there is some bit of slag produced in FCAW.

The slag covers the hot weld pool and is removed after cools. The slag is where impurities that have been removed by the flux go. As such, you can expect slag after flux core welding.

MIG welding also produces some bit of slag. However, the slag produced in this welding technique is lighter and easier to brush away.

When it comes to spatter, both do produce spatter. Spatter is created when the welding wire sends spots of the molten metal around the weld area. The amount of spatter produced depends mostly on the kind of shielding gas used. 

Using carbon dioxide shielding gas is known to produce more spatter. And overall flux core welding does produce more spatter.

Comparing the weld quality

Another topic of debate in the mig welding vs flux core battle is which process has a better weld quality. There are those that claim MIG is better in terms of weld quality but is this true? Well, it all depends on what you consider to be a quality weld.

Strength is used as a measure of weld quality. Both welding techniques do produce strong welds. It is in the appearance of the weld that the two differ. While both can produce good looking welds, it is easier to achieve a beautiful looking weld with MIG.

In the hands of a novice, it can be challenging to produce a clean and aesthetically pleasing weld with flux core welding.

Which offers a better metal penetration

When it comes to penetration, some hold the opinion that flux-cored welding offers a better metal penetration. But how true is this? Generally speaking, metal penetration depends on several things.

First is the amperage and voltage of your welder and second the thickness of the metal. When using a 140v welder with a flux core wire of .030, you can weld steel of up to 4.8 mm thick. When the same welder is used with a solid MIG wire of the same diameter, you can weld steel of up to 1/8 inch.

In essence, with flux core wire, you can weld thicker metals for less amperage compared to MIG. Thus in terms of metal penetration, there some truth in the assumption that flux core wire offers more penetration.

Which metals can I weld using FCAW and MIG?

Question, which metals can you weld with flux core welding? Answer, most ferrous metals. These include copper, stainless steel, mild steel, carbon steel, among others.  For MIG welding, you can weld both ferrous and non-ferrous metals.

While FCAW can weld stainless steel, MIG welding is better at it. In regards to non-ferrous metals such as aluminum MIG welding has the edge over FCAW. Flux core wires are not designed to weld non-ferrous metals.

So in this fcaw vs gmaw battle category, MIG welding comes out on top.

Which is cheaper?

Pound per pound flux core wires is more expensive compared to MIG solid wires. But does this mean MIG is the cheaper of the two? Not quite, MIG welding requires additional equipment that can increase its cost.

For starters, you need to purchase a pressure gas tank. Also, you need to have all the components that come with a pressure tank. A regulator or flow meter and hose are necessary. For flux core, especially these equipment are not needed.

In essence, when all factors are considered, MIG welding is the costlier of the two.


Ordinarily, the voltage of the machine you should use depend on the thickness of the metal you are welding. For thicker metals that may require higher amperage to weld, a higher voltage may be needed.

However, this is mostly for MIG welding. Flux core welding does a better job of welding thicker metal at a relatively lower voltage and amperage.


Both welding techniques can use either both an AC and DC power source. However, DC polarity is recommended. With AC you get an unstable arc and more spatter. For flux-cored welding, Direct Current Electrode Positive polarity is best.

This is where the positive terminal is hooked to the electrode. The result is the electrons flowing in a reverse direction. The same polarity works for MIG welding with solid wire.

Power supply

MIG may require more power to weld than flux core. This is especially when you are welding thicker metals, such as with a thickness of 4.8mm.

Welding position: Flux core welding is mainly used for out of position welding. This is where the welding is done in any other position other than flat or horizontal. Particularly for overhead welding, flux core is the better option.


In this assessment of flux core welding vs mig, it is clear that each technique is suited to different welding applications. Therefore, it is clear that in this mig vs flux core welding battle, there is no clear winner.

When choosing between the two, it is essential to evaluate your needs. What metal you are welding and the welding environment. Flux core is more suited to outdoor welding, while MIG welding is suited to indoor welding.

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