MIG welding feeds a consumable wire through the gun, so it is faster, easier to learn and better on thick steel. TIG welding uses a tungsten electrode that does not melt and a filler rod you feed by hand, so it is slower and harder but gives cleaner, more precise welds on thin metal, stainless and aluminum.
Neither process is better in general. They fit different jobs. This guide covers how each one works, what gas each needs, where each fits on steel framing and fabrication, and how to pick between them.
How MIG and TIG Work
Both are arc welding processes that use an inert or active shielding gas to keep air out of the molten puddle. The difference is what the electrode does.
MIG (GMAW): the wire is the electrode and the filler
MIG stands for metal inert gas. Its formal name is gas metal arc welding (GMAW). A spool of solid wire feeds continuously through the gun. The arc runs between the tip of that wire and the work, and the wire melts into the joint as filler. You pull the trigger, set the travel speed and the machine keeps feeding wire. One hand runs the gun, which is why MIG is easy to use in awkward positions.
TIG (GTAW): the electrode does not melt
TIG stands for tungsten inert gas. Its formal name is gas tungsten arc welding (GTAW). The arc comes from a tungsten electrode that is not meant to melt. If the joint needs filler, the welder dips a separate rod into the puddle by hand. Most setups also use a foot pedal to control amperage, so TIG takes two hands and a foot. That extra control is where its precision comes from, and also why it is slow and hard to learn.
MIG vs TIG Side by Side
The comparison below follows the technical FAQ MIG vs TIG Welding from TWI (The Welding Institute), checked October 2026.
| Factor | MIG (GMAW) | TIG (GTAW) |
|---|---|---|
| Electrode | Consumable wire, machine fed | Non-consumable tungsten |
| Filler | The wire itself | Separate rod, fed by hand (or none) |
| Typical shielding gas | 75% argon / 25% CO2; pure argon for aluminum | 100% argon |
| Typical gas flow | 35 to 50 cubic feet per hour | 15 to 25 cubic feet per hour |
| Speed | Fast, higher deposition | Slow, lower deposition |
| Best thickness | Thicker, larger parts | Thin parts prone to burn-through or warping |
| Out-of-position work | Easier, one-handed | Harder; best on a bench |
| Learning curve | Easier to learn | Harder, needs a skilled welder |
| Appearance and cleanup | More spatter, more cleanup | Little spatter, light polishing |
| Cost per foot of weld | Lower | Higher |
Why no CO2 in TIG gas? TWI notes that CO2 promotes oxidation of the tungsten, which wears the electrode and contaminates the weld. MIG tolerates CO2, and a pure CO2 shield is sometimes used to save money and gain penetration.
When MIG Is the Better Choice
MIG wins whenever speed and thickness matter more than looks. Common examples:
- Shop fabrication of steel members. Welding clip angles, base plates, stiffeners and cap plates to beams and columns is long, repetitive work on plate that is often 1/4 inch or thicker. That is MIG’s strength. Our guide to the structural steel fabrication process shows where welding fits between cutting, drilling and coating.
- Trailers, racks, frames and repairs in mild steel, where the weld will be painted anyway.
- Beginners. TWI calls MIG the better starting point for less experienced welders. You can get a sound fillet weld on clean steel after far less practice than TIG needs.
- Overhead and vertical joints, because one free hand helps you brace and see.
MIG with solid wire and gas is a shop process. Wind blows the shielding gas away, so outdoor and erection-site welding is often done with gasless flux-cored wire or stick electrodes instead. Those are separate processes with their own procedures.
When TIG Is the Better Choice
- Thin sheet and tube that would burn through or warp under a MIG arc.
- Stainless steel, especially where appearance or corrosion resistance matters, such as handrails, food equipment and exposed architectural work. Heat control is the main concern on stainless; see welding stainless steel: filler metals and heat control.
- Aluminum and other non-ferrous metals, where TIG is often preferred.
- Root passes on pipe and other joints where penetration has to be controlled closely.
- Visible welds that will not be ground or painted.
Prep, Coatings and Mill Scale
Both processes need clean metal, but TIG needs it much more. The TIG puddle is small and slow, so oil, paint, rust or scale on the joint gets trapped as porosity or contamination. With MIG you can sometimes get away with less, but a weld over dirt is still a weaker weld.
- Hot-rolled steel comes with a dark oxide skin. Grind it back to bright metal where the weld goes. Our explainer on what mill scale is and how to remove it covers the methods.
- Galvanized steel gives off zinc fume when welded with either process. Remove the coating at the joint and ventilate. See how to weld galvanized steel safely.
- Stainless should be cleaned with stainless-only brushes and grinding discs so carbon steel particles do not rust on the surface later.
Structural Welding Is a Code Question, Not a Process Preference
On a building, the choice between MIG, TIG, flux-cored or stick is not up to whoever holds the gun. Structural steel welding in the US is normally done to the AWS D1.1 Structural Welding Code – Steel, published by the American Welding Society. The engineer of record specifies the weld type and size on the drawings. The fabricator then welds under written procedures, with qualified welders, using a process and filler permitted for that joint.
Weld sizes and types appear on shop drawings as welding symbols. If you are reading a fabrication drawing, our guide on how to read a welding symbol explains the arrow side, other side and fillet size notation. Whether a beam-to-column weld is enough for the load is an engineering question. A licensed structural engineer has to size and check any weld that carries structural load. A home welder should not guess at it.
Fumes and Safety
Both processes produce UV radiation strong enough to burn skin and eyes, so use a proper auto-darkening helmet, gloves and covered skin for either one. Both also produce fume. MIG makes more of it because it deposits more metal. Stainless fume can contain hexavalent chromium, and galvanized steel gives off zinc oxide. OSHA’s welding, cutting and brazing safety topic page covers the fume and gas hazards and the controls. Use local exhaust or a respirator suited to the material, and do not weld coated or unknown metal in a closed garage.
How to Choose
- Mostly mild steel 1/8 inch and thicker, painted afterward: MIG.
- Mostly thin stainless, aluminum or show-quality welds: TIG.
- Learning to weld on a budget: MIG first. TIG later if your work needs it.
- Welding outside in wind: neither gas-shielded process works well. Look at flux-cored or stick.
- Welding anything structural: follow the drawings and the code. The process is set by the welding procedure, not by personal preference.
Many machines sold now are multiprocess units that can run MIG, TIG and stick from one power source. They still need different torches and gas setups for each process.
MIG vs TIG Welding FAQ
Is TIG stronger than MIG?
TWI says TIG welds are typically stronger and more precise. In practice, a properly made MIG weld on steel can still meet the strength the design requires. What matters is correct size, fusion and the right filler for the base metal, not the process name.
Which is easier to learn, MIG or TIG?
MIG. The machine feeds the wire, and you control one gun with one hand. TIG means coordinating the torch, the filler rod and usually a foot pedal at the same time.
Can you use the same gas for MIG and TIG?
Only pure argon works for both, for example MIG on aluminum and TIG on most metals. The common 75/25 argon-CO2 MIG mix should not be used for TIG, because the CO2 attacks the tungsten electrode.
Is MIG or TIG better for welding steel beams?
For shop work on beams, columns and plates, MIG and flux-cored are far more common because they are faster on thick material. TIG is rarely used on heavy structural members. Structural welds are governed by AWS D1.1 and the engineer’s drawings either way.
Why is TIG welding more expensive?
It lays down metal more slowly, needs more joint preparation, and takes more experienced welders. All three raise the cost per foot of weld.
Reference information only, not engineering advice. Disclaimer.