MIG vs TIG Welding Aluminum – Which is Best?

The MIG vs TIG welding aluminum debate has been on for a while when it comes to joining metals. Which one is more suitable for welding aluminum? Can you bond aluminum without welding? What makes a welder’s choice of the two the right one? While they sound similar and can sometimes be confused, MIG welding and TIG welding are unique in their own rights.

MIG and TIG welding aluminum methods are the most common welding choices for aluminum. MIG welding involves the continuous supply of wire electrodes through a welding gun from a motor reel. The TIG welding process uses a welding gun that heats the aluminum metal surface with a tungsten filament; however, the filler metal is supplied with another hand.

After reading this article, you will have a great understanding of the working processes of MIG and TIG welding. You will also get to know the similarities between these two types of welding and their application to welding aluminum.

Ultimately, you will know the many differences, despite their similarities, that exist between them. Further, you’ll find out when it is right to use each of these welding methods in aluminum-based projects.

MIG Welding: A Brief Overview

MIG welding, fully known as Metal Inert Gas welding, or sometimes Metal Active Gas (MAG) welding, is a welding process suitable for bringing metal joints that are either thick or thin. It employs:

• A power source
• Welding gun
• Wire electrodes
• A gas cylinder (usually containing argon, CO2, or a combination of both gases, depending on the nature of the workpiece).

The welding gun is connected to the power source, and another conductor connects the energy that runs from the workpiece back to the power source to complete the power cycle. The welding gun receives a continuous run of wire electrode that also serves as the filling material through a reel supplied by a motor drive.

The gas cylinder supplies gas to the surrounding arc during welding to protect the weld puddle from contamination by environmental gases, such as oxygen, that may cause corrosion.

The process of MIG welding is usually automatic when there is no need for manual adjustment or movement of the welding gun along the joint. However, in most cases, the workpiece has to be adjusted to ensure neat joinery and finish, making the process semi-automatic.

MIG welding is commonly used for different metals, ranging from steel – carbon and stainless – to aluminum.

TIG Welding: A brief Overview

TIG, or Tungsten Inert Gas welding, is an arc welding process similar to MIG welding. The difference is that TIG welding does not use a consumable electrode to form the weld puddle when the filler material and base metal melt.

TIG welding employs a power source that helps provide electric current when the electrode forms an arc with its position to the workpiece. It uses an electric current to create heat on the workpiece through the non-consumable electrode. It combines the filler material and parent metal in a weld pool that solidifies to form metal joinery.

Tungsten’s name claims to be derived from the fact that the electrode doesn’t become consumed by heat, unlike tungsten filaments in incandescent bulbs.

TIG welding uses precision welding to join metals by introducing the filler material into the weld pool while being protected by the inert gas from the gas cylinder to prevent reaction with contaminants from the environment. The process of using a TIG welder is seldom automatic as the filler material has to be supplied using a free hand while the welding gun delivers current to the workpiece.

This welding method is commonly used to join metals such as aluminum as it provides better finishes, a more precise weld, and doesn’t cause a burn-through on them.

Differences Between MIG and TIG Welding

MIG and TIG welding are both types of arc welding techniques that employ electric current – AC or DC – to heat the workpiece and supply filler material into the weld pool while protecting it from the influence of environmental contaminants. Although they reach the same goals, they do so differently, as we will soon see.

The processes involve the use of power, the supply of inert gases, the supply of filler material, and the speed of the supply, all with different equipment. We will see how these parameters and equipment differ in their operation and how they influence the application and efficiency of each of these welding methods.

Operation Process

The operation processes of these two methods are somewhat similar. Both techniques involve using electrodes to create heat as electric current passes through the electrodes and melts the parent metal, and needs an arc between the electrode and the workpiece, to create the melt pool. However, these similarities in operation processes are used differently.

MIG welding uses wire electrodes passed from the reel of a motor drive and through the welding gun. The direct electric current passes to the wire electrode through the copper contact tip, which also helps to reduce spatter during welding. The motor drive continuously supplies the wire electrode while it melts the workpiece and supplies the filler metal simultaneously. The gas nozzle on the welding gun supplies gas, usually argon, that protects the melt pool from oxygen, thereby preventing corrosion.

However, though it uses either DC or AC electric current, the TIG welding process follows a different pathway. The tungsten electrode receives current from the power source and heats the workpiece, melting the parent metal due to heat created when an arc is formed with the metal and current is generated. The filler metal is supplied separately, unlike in MIG welding, and the welder has to maintain a continuous line along the weld path as the current remains constant.

From these operation processes, it is evident that there is a difference in their power source. While MIG depends on DC, TIG can operate on both AC and DC. Also, MIG is almost automatic except when the welder has to move the welding gun along the joint line by himself. On the other hand, TIG welding needs a manual supply of filler metal to the melt pool, making it an almost manual operation.  

Equipment

The welding equipment generally includes a power source that supplies either DC or AC, or both types of current, a welding gun, electrodes, a filler rod, and sometimes, gas cylinders. In some cases, the cylinders may not be needed, especially if the melt pool is readily coated for protection against corrosion.

MIG welding uses all of this equipment. It uses gas cylinders that contain argon gas, carbon dioxide, or a combination of both gases. It also uses a welding gun that holds the electrode and gas nozzle. Its electrode is usually a wire electrode that is cored wire or solid wire. It is common to find steel wires that are coated with copper. The gas cylinder is also an essential part of the equipment setup for MIG welding. The operation process begins with the pressing of the switch on the gun.

TIG welding uses all the equipment mentioned above. It uses a welding gun with a switch and carries the electrode that heats the workpiece. However, unlike MIG welding, TIG welding uses a different filler metal usually introduced into the weld pool when operation begins. Current passes to the workpiece and melts it when the tungsten electrode creates an arc with the parent metal. Gas nozzles are present around the electrode and shield the weld pool from corrosion.

The difference in the equipment is evident in the electrode and welding gun. While MIG welding uses a consumable electrode that melts and becomes part of the weld pool, TIG welding’s electrode does not melt; that is, it is not consumable. Also, the welding gun in MIG welding accepts an automatic supply of wire, while the TIG welding gun accepts no such thing.

Speed

The speed at which a welder can complete an aluminum-based project depends on which type of welding he chooses. MIG vs TIG welding aluminum are similar in many respects but differ in the speed of accomplishing their objective. While the former is faster, the latter is slower due to the nature of their processes.

MIG welding supplies consumable electrode and filler material through an automatic process, made possible by the motor drive that reels the wire electrode to the welding gun. The speed at which the motor supplies wire electrodes to the welding gun is the wire-feed speed. However, the rate at which the wire electrode is deposited on the parent metal is called deposition rate. Although the wire-feed speed influences the deposition rate, it does not affect how fast a welder finishes a welding project.

TIG welding uses non-consumable electrodes, and the filler metal used for this operation is usually supplied by hand. Therefore, the speed of completing a metal welding project using TIG welding depends on the speed of travel of the welding gun and the hand holding the filler metal.

In essence, MIG welding is a faster method to complete a welding project than TIG welding, provided the project is of the same size. MIG owes its speed to the fact that it is semi-automatic and suitable for use in thin and thick metal joinery. However, ensure that the wire-feed rate is not so low that it affects the travel speed.

Finishing Appearance

The smaller the welding beads, the better the finish. Also, the less the amount of weld pool, the better the finish. This applies to both of them as they both employ a weld pool to fix aluminum joints. However, since they are both suitable for use in many metals, including aluminum, it only makes sense that a welder chooses one that suits the project’s purpose. Therefore, for a neat welding finish, TIG welding is preferable.

TIG welding does not always need filler metal as it melts the parent metal and fills the joint with the molten material. However, if there is a need for filler material, it is applied as little as is needed, eliminating the need for removing extraneous filler.

On the other hand, MIG welding can have more than enough filler metal, depending on the wire-feed speed. Also, it is common for splatter to occur when using MIG welding.

 TIG is the clear winner for the finishing appearance round as it is generally neater.

Filler and Filler Replacement

In joining metals, there is a high chance that you will need filler material. Depending on the thickness of the metal and on exhaustion of the material, you will need to replace it. Depending on the type of welding you are practicing, there may be a disruption in the smoothness of your weld bead when you stop and start. However, the irregularity can be unnoticed by some.

MIG welding follows a semi-automatic process that automatically feeds the wire electrode, which is also the filler metal. As long as the travel speed is maintained, the supply of filler material remains constant throughout the welding process. This means the electrode and filler material is the same, and it is only replaced when the wire electrode is exhausted from the reel that supplies it.

With TIG welding, the filler material is separated from the electrode. The electrode is non-consumable, while the filler material is consumed as it is melted to become part of the weld pool. The electrode needs no replacement as in the MIG welding, while the filler material needs to be replaced when used up, which is often the case, depending on the length of the joinery.

MIG welding can be taken as the winner as it takes longer to exhaust the filler material. However, TIG welding can be the winner, too, as it is easy to replace the filler material when the need arises.

Ease of Use

MIG welding uses all the equipment that is needed for welding, as does TIG welding. They both deliver in their applications and have similar equipment setups. However, they are different in some respects, making their ease of use further.

MIG welding employs a consumable electrode that is thin and can vary in size, depending on what is needed for the project. However, the consumable electrode is quickly passed and used to apply to the parent metal and weld pool with the same hand. This is because the wire electrode and the filler metal are the same, one coating the other. This makes it suitable for use in many applications and easy for beginners to use.

However, TIG welding uses non-consumable electrodes, which is an advantage as welders do not have to change electrodes when they get used up continually. What needs change in the TIG welding equipment setup is the filler metal. This poses a problem for beginners as it may disrupt the smooth flow of welding beads.

The easiest welding method is MIG welding, and it is the clear winner.

Nature of Material

The nature of the material in this sense refers to the thickness of the base metal. Both MIG and TIG welding can join different kinds of metals ranging from stainless steel to carbon steel and aluminum. However, they are best suited for other metals.

MIG welding is more suitable for use in metals that have high thickness and need filler material to strengthen the joints of the metal as in big pipes. It is, therefore, more commonly used with carbon steel and stainless steel.

On the other hand, TIG welding can be used without filler material, making it suitable for use in thin metals. It is more commonly used in aluminum and metals that need fine finishes. It provides this aesthetic quality by using as little weld pool as possible. It can melt only the base metal, which solidifies and strengthens the joint.

There is no clear winner in this bout as each welding type is best suited to different kinds of materials, even though you can use them outside their recommended usage.

Metal Transfer Modes

Metal transfer mode refers to how the welding gun makes filler metal available to the weld pool and solidifies when joining metals. It varies from one welding type to the other and dramatically influences the quality and appearance of welding.

MIG welding has different metal transfer modes, all of which have their peculiarity. The correct metal transfer mode must be employed to get the best weld quality and appearance. The four metal transfer modes in MIG welding are:

Globular Mode

This mode of metal transfer combines short circuits and dependence on gravity to drop solid wire or metal-cored wire on the surface of the workpiece. The electrode does not have to be in contact with the base metal for this metal transfer to take place.

It is a fast way of achieving welds and employs inexpensive materials such as carbon dioxide as the shielding gas. However, it is not suitable for cleaning and even finishes.

Short-Circuiting Mode

Also called the Dip Mode of metal transfer is the use of filler metal on the workpiece by employing repetitive electric short circuits. It uses low heat and works only when the electrode is in contact with the parent metal. It creates short and relatively clean weld beads, although it employs a slower travel speed than globular mode.

It can join metals in different positions, including verticals, and is easy to use. Also, you can accomplish at least 93% electrode efficiency with it.

Spray Mode

As the name implies, it is a not-so-neat method of introducing filler metal to the weld pool. Although it can achieve 98% electrode efficiency, it produces regular droplets, accounting for better aesthetic results.

This mode of metal transfer employs high energy to feed wire electrodes and filler metal to the welding pool in tiny droplets. The deposition rate is high, less spatter during welding, and easy to clean after welding.

Pulsed Mode

Considered the best metal transfer mode in MIG welding, the pulsed mode employs high and low currents to transfer cored wire and solid wire electrodes to the weld pool. It achieves smooth and regular weld beads with great consistency and has 98% electrode efficiency.

This metal transfer mode discourages splatter and can easily be automated.

In TIG welding, the metal transfer mode only happens when the filler metal enters the weld pool. Unlike in MIG welding, TIG has only one metal transfer mode.

Safety

Welding is an occupation that requires a high level of concentration and skill. But when you are doing the job, safety should be at the forefront of your mind. It is a process that can be dangerous if not done correctly. It can also be dangerous if you’re not wearing the appropriate safety equipment. When welding, there are some basic safety precautions to take:

• Make sure the work area is clean and free of debris.
• Stay away from sparks.
• Wear appropriate clothing and gloves for your task (i.e. blankets, a long-sleeved shirt, gloves, eye protection, steel-toed boots).
• Always use a welding helmet.
• Use approved welding equipment with oxygen-less cutting wire or an approved welding torch.
• Know what you’re doing.

Frequently Asked Questions

Conclusion

MIG and TIG welding are types of arc welding that use a similar process to achieve metal joinery, using electrodes and filler metal. They are identical in many respects and can be used interchangeably, sometimes. However, they are not the same and are best suited for different metals.

A MIG welder uses a consumable electrode to create an arc with the workpiece and generates heat to melt the parent metal into the filler metal, solidifying when the weld pool cools.

TIG welding uses a non-consumable electrode, called a tungsten electrode, that heats the workpiece by creating an arc with its surface and melting it. It may use filler types of metal but can also use the same base material to create metal joints. It uses both DC and AC electric current as power.

In both MIG and TIG welding, gas cylinders must provide gas that shields the weld pool from contamination. Usually, carbon dioxide, argon, or a combination of both, is used for this purpose.

However, in the MIG vs TIG aluminum welding bout, TIG is the preferred welding method due to its finesse in welding thin metals. However, if the aluminum material is thick, it is better to use MIG welding.