The difference between MIG and TIG welding comes down to the electrode. MIG melts a wire into the joint, TIG uses a tungsten electrode that does not melt.
Everything else follows from that: speed, weld appearance, heat input and cost. Both are among the most used welding processes in machine and plant construction.
This guide explains the abbreviations MIG, MAG and TIG, compares the processes point by point and shows when each one is the right call. For the basics, see our guide to what welding is.
Key Takeaways
- MIG and MAG differ only in shielding gas. Most structural steel is actually welded MAG, not MIG.
- MAG is fast and economical, TIG is precise and visually clean. That is the real trade-off.
- Aluminium is TIG welded on AC, because alternating current breaks up the oxide layer.
- Lift TIG is an ignition method, not gasless welding. TIG is impossible without shielding gas.
- TIG filler is optional. On thin sheet, autogenous welding fuses the parent material alone.
- In practice the two are often combined: a TIG root with MAG fill passes.
Table of Contents
- MIG, MAG, TIG and GTAW: what the abbreviations mean
- What is MIG welding?
- MIG or MAG? The difference most people miss
- What is TIG welding?
- MIG vs TIG side by side
- Equipment: what a TIG welding machine needs to do
- Which process for which metal?
- Decision guide: when to use MIG, when to use TIG
- Typical use cases in industry
- Qualification: what makes a TIG welder
- Other processes worth considering
- Welding at Vulcanus Stahl
- Frequently asked questions
MIG, MAG, TIG and GTAW: What the Abbreviations Mean
The terminology causes constant confusion, because trade names, standards designations and national variants all circulate side by side. This table sorts them out.
| Abbreviation | What it stands for | Process no. per ISO 4063 |
|---|---|---|
| MIG | Metal Inert Gas | 131 |
| MAG | Metal Active Gas | 135 |
| GMAW | Gas Metal Arc Welding, the umbrella term for MIG and MAG | 13 |
| TIG | Tungsten Inert Gas | 141 |
| GTAW | Gas Tungsten Arc Welding, the same process as TIG | 141 |
| WIG | Wolfram-Inertgas, the German name for TIG | 141 |
| MMA | Manual Metal Arc, stick welding | 111 |
What does TIG stand for?
TIG stands for Tungsten Inert Gas, tungsten being the non-consumable electrode material. The formal designation is GTAW, and in standards the process is number 141.
If you work with German drawings or welding procedure specifications, you will see the same process written as WIG, short for Wolfram-Inertgas. Wolfram is simply the German word for tungsten.
What does MIG stand for?
MIG stands for Metal Inert Gas. Inert means the shielding gas does not react with the weld pool, typically pure argon.
Where an active gas such as CO2 is used instead, the process is called MAG. Together they fall under the umbrella term GMAW.
What Is MIG Welding?
In MIG/MAG welding a wire is fed continuously through the torch. That wire is both the electrode and the filler metal.
Shielding gas flows from the same nozzle and protects the weld pool from oxygen and nitrogen. Because the wire feeds itself, the welder only needs one hand.
That makes the process fast, easy to automate and comparatively quick to learn.
Advantages
- High deposition rate: long welds and thick sections can be joined economically.
- Easy to automate: well suited to series production and robotic cells.
- Short learning curve: usable results are achievable within a few weeks.
- Low cost per metre of weld: speed and lower labour input both work in its favour.
Disadvantages
- Spatter: inherent to the process and it costs cleaning time. Our guide explains how to prevent weld spatter.
- Higher heat input: more distortion on thin or slender components.
- Less fine control: the process reaches its limits on visible welds and very thin sheet.
MIG or MAG? The Difference Most People Miss
MIG and MAG are technically almost identical. The only difference is the shielding gas.
MIG runs on inert gas, meaning pure argon or an argon-helium mix. It is used mainly on aluminium and non-ferrous metals.
MAG runs on active gas, usually a mixture of roughly 82 per cent argon and 18 per cent CO2. The CO2 reacts in the arc and improves penetration on steel.
In practice this means: when people say MIG welding on steel, they almost always mean MAG. True MIG is reserved for aluminium and special materials.
The CO2 has a downside, though. It makes metal transfer coarser and raises spatter, particularly in the upper power range.
What Is TIG Welding?
In TIG welding the arc burns between a tungsten electrode and the workpiece. The electrode itself does not melt.
Filler metal is fed as a rod with the second hand, in measured amounts and only where it is needed. The shielding gas is pure argon.
On very thin sheet the process can run with no filler at all. This autogenous variant fuses only the parent material and produces exceptionally narrow welds.
Advantages
- Outstanding weld quality: clean, even welds with no spatter and usually no finishing.
- Very fine heat control: ideal for thin, heat-sensitive and high-alloy materials.
- Full control: current and filler are controlled independently of one another.
- Ideal for visible welds: wherever appearance matters as much as function.
Disadvantages
- Considerably slower: rarely economical for long welds or high-volume work.
- High skill requirement: two-handed operation with a long learning curve.
- Sensitive to contamination: the joint area and filler rod both have to be clean.
MIG vs TIG Side by Side
The table below covers the differences that actually decide the process choice in production.
| Criterion | MIG and MAG (131 / 135) | TIG (141) |
|---|---|---|
| Electrode | consumable wire, also the filler | non-consumable tungsten electrode |
| Filler metal | fed automatically by the wire drive | fed by hand, or omitted entirely |
| Shielding gas | argon, argon-CO2 mixtures or pure CO2 | pure argon, sometimes with helium |
| Power source | constant voltage, usually DC electrode positive | constant current, DC or AC |
| Deposition rate | high, in the order of several kg per hour | low, usually well under 2 kg per hour |
| Spatter | inherent to the process | virtually none |
| Weld appearance | good, normally needs finishing | excellent, often needs none |
| Heat input | higher, more risk of distortion | low and finely controllable |
| Material thickness | from about 1 mm, excellent on thick sections | from about 0.5 mm, ideal on thin parts |
| Learning curve | workable results within weeks | needs considerably more practice |
| Automation | very well suited | good, usually orbital or robotic |
| Cost per metre of weld | low | higher, through time and skill |
Three things a table cannot show. First, the higher heat input of MAG welding alters the heat-affected zone more, which matters on quenched and tempered materials.
Second, MAG welding regularly means finishing work afterwards. The methods for that are set out in our guide to weld cleaning.
Third, the two processes are not mutually exclusive. On pipework, a TIG root with MAG fill passes has been standard practice for decades.
Equipment: What a TIG Welding Machine Needs to Do
With TIG, the machine matters more to the result than it does with MAG. Four points carry most of the weight.
DC or AC
Steel and stainless steel are welded on direct current, electrode negative. Aluminium needs alternating current, because AC breaks up the tenacious oxide layer.
A DC-only machine therefore cannot weld aluminium at all. If you need both, you need an AC/DC machine with an adjustable balance control.
Ignition: high frequency and lift arc
High-frequency ignition starts the arc without contact and protects the electrode tip. Lift arc ignites by touching down briefly and lifting away.
Lift arc makes sense where high frequency could disturb nearby electronics. It is an ignition method, not a way of welding without gas.
Tungsten electrodes
The electrode is chosen by material and current type, and is identified by a colour code. Common grades are WT20 in red, WC20 in grey, WL15 in gold and WP in green.
The grind matters just as much. A sharply ground tip focuses the arc, while a rounded tip spreads the heat more widely.
Torch and accessories
Above moderate currents, water-cooled torches are essential. For the available designs see our guides to welding torches and specifically to TIG torches.
A foot pedal, or a torch trigger with up-slope and down-slope, lets the welder vary current during the weld. On visible welds that is what makes the difference.
Protective equipment belongs in the same conversation. See our articles on welding hazards and on welding fume extraction.
Which Process for Which Metal?
Material is the strongest single selection criterion. For filler metal choices, see our overview of welding materials.
| Material | Recommended process | Note |
|---|---|---|
| Structural steel, thick section | MAG (135) | M21 mixed gas, roughly 82 per cent argon and 18 per cent CO2 |
| Structural steel, thin section | MAG short arc, or TIG | prefer TIG where the weld will be visible |
| Stainless steel | TIG, MAG in volume production | plan root shielding with forming gas |
| Aluminium | TIG on AC, or MIG (131) | AC breaks up the tenacious oxide layer |
| Titanium and magnesium | TIG only | full gas coverage is mandatory, root side included |
| High-strength steels such as S 960 QL | MAG or TIG, depending on the joint | match heat input and filler metal carefully |
| Nickel-base alloys | TIG | low dilution and clean process control required |
With aluminium, preparation matters as much as the process. Our guide to welding aluminium sets out what to watch.
With stainless steel, the root side decides the corrosion resistance. Without forming gas the root oxidises and the passive layer suffers, as explained in our article on which metal does not rust.
High-strength and creep-resistant steels need preheating and often post-weld heat treatment of metals. EN 1090 and ISO 3834 remain the governing standards.
Decision Guide: When to Use MIG, When to Use TIG
The question is never which process is better. It is which one fits the material, the tolerance and the batch size.
| If your project … | then … |
|---|---|
| has long welds on thick structural steel | MAG |
| runs in series with a short cycle time | MAG, ideally automated |
| involves sheet under 2 mm | TIG |
| needs visible welds with no finishing | TIG |
| is made of aluminium or titanium | TIG, on AC for aluminium |
| involves pressurised or root-welded pipe | TIG root, MAG fill passes |
| must hold very tight distortion limits | TIG, or a cold process such as CMT |
| needs the lowest cost per metre of weld | MAG |
The short version: MAG when volume and material thickness dominate. TIG when accuracy, appearance or the material demand it.
Typical Use Cases in Industry
Structural and load-bearing steelwork
On bridge supports, crane frameworks and industrial platforms, MAG dominates. It lays down deep-penetrating welds quickly on thick steel profiles.
On safety-critical joints under cyclic load, TIG takes over. Its finer heat control reduces undercutting and micro-cracking.
Machine and plant construction
For machine frames and custom equipment, the hybrid approach is the norm. MAG for large load-bearing structures, TIG for flanges, mounting plates and hydraulic interfaces.
What happens to welded assemblies afterwards is covered in our guide to assembly manufacturing.
Pressure vessels and heat-exposed components
On tanks, furnace parts and steam systems, the root pass is laid in TIG. It is the only reliable way to guarantee pore-free, fully penetrated welds.
These components are often heat-resistant steels or high-nickel alloys. Here weld integrity governs not just performance but regulatory approval.
Qualification: What Makes a TIG Welder
Good TIG welds are not luck, and they are not a function of the machine. They are the product of qualified people and qualified procedures.
Welders are approved to ISO 9606-1, each within a defined range covering process, material group, joint type and position. An approval in TIG does not cover MAG.
The procedure itself is qualified separately. A procedure test to ISO 15614 produces a WPQR, from which the welding procedure specification, or WPS, is derived.
Whether the weld actually holds is then proven, either non-destructively or by destructive testing. For load-bearing components that chain is mandatory, not optional.
Other Processes Worth Considering
MIG and TIG do not cover every case. These alternatives are worth a look when both reach their limits.
- CMT welding: very low heat input on thin sheet and dissimilar joints.
- Laser beam welding: narrow welds, minimal distortion, high speed, high equipment cost.
- Orbital welding: mechanised TIG for repeatable circumferential welds on pipe.
- Electrode welding: needs no shielding gas, so it wins outdoors and in wind.
- Plasma welding: a more tightly constricted arc than TIG, deeper penetration in a narrow weld.
- Robotic welding: consistent quality in series work, usually MAG based.
Welding at Vulcanus Stahl
Vulcanus Stahl is a recognised welding company to DIN EN 1090-2 EXC3 and DIN EN ISO 3834-2. Our quality management system is certified to ISO 9001.
We manufacture welded assemblies for machine and plant construction up to 10 t piece weight. High-strength materials such as S 960 QL and heat-resistant steels are processed daily.
Our welding services include:
- MAG, MIG, TIG and manual arc welding for steel, stainless steel and aluminium
- hybrid joint concepts with a TIG root and MAG fill passes
- approved welders and documented welding procedure specifications per component group
- welded assemblies for large parts, with machining afterwards in house
- one-offs, small batches and series work in CNC contract manufacturing
Because welding, machining and assembly all sit under one roof here, the process choice is made early rather than late. The full capability list is under our services.
Not Better or Worse, but Fit for Purpose
MIG and MAG stand for speed, economy and thick sections. TIG stands for accuracy, clean appearance and sensitive materials.
Choosing on material, tolerance and batch size rather than habit saves both rework and money. In many cases the right answer is to use both.
Vulcanus Stahl delivers certified welded assemblies and precision manufacturing from a single source. Talk to our welding team about your next project.
Frequently Asked Questions About MIG and TIG Welding
- What does TIG stand for in welding?
Tungsten Inert Gas. The formal designation is GTAW and the standards process number is 141. German documents call the same process WIG.
- What does MIG stand for?
Metal Inert Gas. Where an active gas is used instead of an inert one, the process is called MAG.
- What is the difference between MIG and MAG?
Only the shielding gas. MIG uses inert gas such as pure argon, MAG an active mixture containing CO2. Structural steel is mostly welded MAG.
- Can you do lift TIG welding without gas?
No. Lift TIG only describes the ignition method, touching down and lifting away. Without shielding gas the weld pool oxidises immediately and the tungsten electrode burns back.
- Which process is easier for a beginner?
MIG and MAG. The wire feeds automatically, so one hand is enough. TIG requires two-handed coordination and far more practice.
- Can aluminium be MIG welded?
Yes, with pure argon and a suitable wire drive. For thin parts and visible welds, TIG on AC is the better choice.
- What should a TIG welding machine be able to do?
DC is enough for steel. Aluminium requires an AC/DC machine. Pulse mode, up-slope and down-slope and a foot pedal are all worth having.
- What qualification does a TIG welder need?
Welder approval to ISO 9606-1 for the relevant range. For load-bearing components a procedure qualification and a written WPS are required as well.