Almost every week someone asks whether their job should be MIG or TIG welded, usually because they have read that TIG is "better." It is not better. It is different, and it is slower, and slower costs money. Here is how we actually pick between them on the shop floor.
The short version
| MIG (GMAW) | TIG (GTAW) | |
|---|---|---|
| Speed | Fast. A skilled welder runs 8–12 inches a minute on ¼" steel. | Slow. Roughly a third to a quarter of MIG speed. |
| Best on | Carbon steel ⅛" and up, production runs, structural work | Thin material, stainless, aluminum, anything cosmetic or sanitary |
| Appearance | Good. Some spatter and a rougher bead profile. | Excellent. Clean, uniform, often no clean-up needed. |
| Cost | Lower labor per foot | Higher labor per foot, sometimes 2–4× |
| Field use | Fine with flux-core wire; sensitive to wind with gas | Difficult outdoors; needs shielding from any draft |
When we reach for MIG
MIG, or gas metal arc welding, feeds a wire electrode continuously through the gun. You pull the trigger and it welds. That makes it fast and repeatable, which is why nearly all structural steel, trailer frames, equipment repair and general fabrication is MIG or its cousin flux-core.
On a stair stringer, a machine base or a dump body floor, the weld needs to be strong, meet the code, and get done. MIG does that. The bead will have a slightly raised profile and some spatter to knock off, and none of that matters once it is primed and painted.
MIG also handles thick material well. With the right wire and voltage we run it on plate over an inch thick using multiple passes.
When we reach for TIG
TIG, or gas tungsten arc welding, uses a non-consumable tungsten electrode to make the arc and a separate filler rod fed by hand. The welder controls heat with a foot pedal and adds filler with the other hand. It is the most controllable process we have, and the slowest.
We use TIG when:
- The material is thin. Sheet under 1/16" burns through with MIG unless the welder is very good and the fit-up is perfect. TIG lets us dial heat down precisely.
- It is stainless that food, product or people will touch. Sanitary tube, dairy frames, restaurant counters. TIG gives a smooth, crevice-free weld that cleans and passivates properly.
- It is aluminum and it needs to look right. Aluminum can be MIG welded, and we do for production truck boxes. But a visible aluminum weld on a boat, a railing or a piece of furniture is TIG.
- The weld is the finish. Architectural railings, brushed stainless, exposed structural members in a lobby. If nobody is painting over it, TIG.
- Code requires it. Most stainless pipe roots and many pressure welds are specified as GTAW.
The mistakes we see
Paying for TIG on structural steel. Someone asks for a TIG-welded trailer frame because it sounds premium. It would cost three times as much and be no stronger. MIG with the right wire and a certified welder is the correct answer.
MIG on sanitary stainless. The opposite mistake. MIG on 16-gauge stainless tube leaves a rough inside surface where bacteria can hold. On product-contact stainless, we TIG with a back purge every time.
Ignoring the environment. A beautiful TIG weld in the shop can be impossible on a windy jobsite where the shielding gas blows away. For field work we often switch to flux-core or stick and design around it.
Rule of thumb: if it will be painted and it is steel ⅛" or thicker, it is MIG. If it is thin, stainless, aluminum, or visible, it is TIG. If it is outside in the wind, ask us.
What about stick?
Stick welding (SMAW) is the old workhorse. Rods, no gas, works in wind and rain, welds through rust and paint that would stop MIG cold. We run it constantly on the mobile trucks for farm equipment, field erection and emergency repairs. It is not pretty and it is not fast, but a stick welder can fix a broken hitch in a muddy field at 6 a.m., and no other process can say that.
Just tell us what it is
You do not need to specify the process when you call. Tell us what the part is, what it does, what it is made of and where it lives. We will pick the process that gets you the strongest weld for the least money, and if you want it done differently, we will explain the tradeoff.