Two arc processes, two different approaches
Both MIG and TIG welding use an electric arc to melt metal, and both usually use a shielding gas to protect the molten pool from the air. The difference lies in how the filler metal gets there and how much control the welder has.
- MIG (metal inert gas, also called GMAW) pushes a continuously fed wire electrode through a hand-held gun. The wire is both the electrode and the filler metal. You pull a trigger and the wire feeds automatically.
- TIG (tungsten inert gas, also called GTAW) uses a non-consumable tungsten electrode to make the arc. The welder adds filler metal separately, with a rod held in the other hand, and often controls the current with a foot pedal or a thumb control.
Stick welding, covered in the article on arc welding, is a third common process, and it uses neither a gas bottle nor a continuously fed wire.
How each one feels to use
MIG is often called the easier process to learn. The wire feeds on its own, so one hand holds the gun and the other can steady it. A beginner can lay down a presentable weld on clean steel after a relatively short time, though good welds still depend on correct settings and technique.
TIG asks for coordination of both hands, and often a foot, while keeping the arc length steady and feeding the rod at the right moment. The learning curve is steeper, and progress can feel slow at first. In return, it gives fine control over heat and the weld pool.
Speed and productivity
MIG is generally faster. Continuous wire means fewer stops to change rods, and the process suits longer welds and repeated production work. TIG is slower, which is acceptable when the priority is precision rather than quantity.
Appearance and quality
A well-made TIG weld has a distinctive neat, uniform look and typically involves little spatter. It is often used where appearance or precision matters, such as thin stainless steel, aluminum and some fabricated art or custom work. MIG welds can be strong and tidy but usually produce more spatter that needs cleanup, particularly with some wire and gas combinations.
Neither process automatically produces a sound weld. Fit-up, cleanliness, settings and technique matter more than the process name.
Materials and thickness
Both processes can weld steel, stainless steel and aluminum, though the equipment and settings differ for each metal.
- MIG is a common choice for mild steel from thin sheet up to thicker plate, and is widely used for automotive and general repair work. Aluminum is possible, but typically needs a suitable setup, such as a different gun arrangement and the right gas.
- TIG is well regarded for thin material and for metals that need careful heat control, because the welder can adjust current while welding.
Machine capacity limits the thickness that either can weld, so check the manual.
Shielding gas and wind
Gas-shielded processes need a cylinder, a regulator and a gas supply. Argon is widely used for TIG. MIG on steel commonly uses argon-based mixtures, and the mix varies with the metal and the result desired. Ask a welding supplier or consult the machine manual for what suits your application.
A draft can blow the shielding gas away and cause porous welds, so gas-shielded welding is usually best done indoors or in a sheltered place. Some MIG setups use flux-cored wire instead, which makes its own shielding and is more tolerant of wind, at the cost of slag and more fumes.
Cleanliness and preparation
TIG is especially sensitive to contamination. Metals should be cleaned thoroughly, and aluminum in particular needs oxide removed before welding. MIG can tolerate slightly more surface imperfection, but clean metal still gives better results, and paint, oil and galvanizing should be removed from the weld area.
Cost and equipment
Neither process is cheap to set up, since each needs a power source, cables, a regulator and gas, plus protective gear. TIG setups are often more involved, with torches, tungsten electrodes and sometimes water cooling or a pedal. Prices vary widely, so compare features rather than assuming that one costs more.
Quick comparison
| Feature | MIG | TIG |
|---|---|---|
| Filler | Continuous wire | Separate rod |
| Learning curve | Gentler | Steeper |
| Speed | Faster | Slower |
| Control | Good | Very fine |
| Cleanup | More spatter | Usually little |
| Wind tolerance | Low with gas, higher with flux-cored | Low |
| Typical use | General fabrication, repair | Thin metal, precision, appearance |
These are general characteristics. Individual machines, wires and welders differ.
Safety is shared
Both processes produce intense light, heat, sparks and fumes. A proper helmet, flame-resistant clothing, gloves and ventilation are required for either, as described in the discussion of protective clothing. TIG makes very bright light even at modest current, and compressed gas cylinders need to be secured upright so they cannot fall.
Take a class if you can, and leave load-bearing or safety-critical welds to qualified welders. This article is general information, not professional advice.