MIG vs TIG welding: which should you specify for your parts?
A buyer's guide to choosing the right welding process for your weldment, by strength, finish, material and budget, plus what to put in your RFQ.
Specifying the wrong welding process is one of the quiet ways a custom part ends up over budget or bounced at inspection. MIG and TIG both make sound welds. They are not interchangeable, and the one you ask for sets the price, the lead time and whether the bead is something you show a customer or hide behind a cover.
Quick answer: MIG is faster and cheaper and is the right call for most structural steel weldments. TIG is slower and more precise and earns its rate on thin material, aluminum, stainless and any weld that has to look clean. Pick the process before you send the drawing, because a shop cannot un-warp a thin stainless panel that got run on a MIG gun to save an hour.
The core difference in one line
MIG (GMAW) feeds a wire electrode continuously and lays metal down fast. TIG (GTAW) uses a tungsten electrode and a filler rod the welder feeds by hand, slower but far more controlled. Speed versus control. Everything below is that one trade playing out.
| Factor | MIG (GMAW) | TIG (GTAW) |
|---|---|---|
| Speed / cost | Fast, lower cost per part | Slow, higher cost per hour |
| Best material | Mild and carbon steel | Aluminum, stainless, thin sheet |
| Thin material | Burns through easily | Controls heat, no burn-through |
| Bead appearance | Functional | Clean, show-surface |
| Typical use | Frames, skids, structural steel | Food/pharma, aerospace, visible work |
When to specify MIG
Structural steel, heavier sections, production runs where cost per part is the number that matters, and anything that gets painted or powder coated so nobody sees the bead. MIG is the workhorse of metal fabrication, and for a mild-steel frame or skid it is the obvious answer. Do not pay TIG rates to weld a trailer frame that lives under a deck plate.
When to specify TIG
Aluminum, stainless, thin wall, and anything the customer will actually look at. Spec TIG for 5052 aluminum enclosures, 316 stainless food equipment, and any panel under about 2 mm that a MIG arc would blow a hole through. It costs more per hour and it is worth it, because the alternative is a warped part and a second setup. If your part is aluminum or stainless, TIG is the default until someone gives you a reason it is not. See welding shops across Canada.
The certification question people fumble
If your fabricator cannot tell you whether your weld falls under CWB certification to CSA Standard W47.1 Division 1 or 2, they are not going to pass the inspection either. Structural steel in Canada generally needs a CWB-certified shop (W47.1 for steel, W47.2 for aluminum, with W59 governing the welded construction). This is not optional on load-bearing work, and it is the first thing an engineer of record checks. Say up front whether your job needs it. The Edmonton and Nisku oil-and-gas shops live and die by this paperwork.
What it costs you to get it wrong
A TIG weldment on a part that never needed the finish is money you set on fire. A MIG weldment on thin stainless is a rejected part and a second run. The cheapest weld is the one done with the right process the first time. A quote that comes back in four minutes was priced off the thumbnail, not your section thickness. The real number lands after someone reads the drawing.
What to put in your welding RFQ
- Material and grade, and section thickness (say 6061-T6 vs 5052, or 304 vs 316)
- Whether the weld is structural, sealed (leak-tight), or cosmetic
- Any finish (paint, powder coat, passivation) so it is quoted as one job
- Certification: CWB W47.1 Division 1 or 2, or aerospace flow-downs, if they apply
- Quantity and timeline
The clearer the spec, the tighter the quote. If you would rather not pick the process, describe what the part has to do and send one RFQ, and we route it to Canadian welding shops that recommend the right approach and quote it.
FAQ
Is TIG always better than MIG?
No. TIG gives more control and a cleaner weld, but it is slower and costs more. For most structural steel weldments MIG is the better value. Which one is "better" depends on the material, the section thickness, and whether anyone will see the weld.
Which is stronger, MIG or TIG?
Both make full-strength welds when done right. Strength comes from process selection, joint prep and a qualified welder, not from MIG versus TIG in the abstract. On thin material and aluminum, TIG is more likely to give a sound weld.
How do you weld aluminum?
TIG for most work, or MIG with a spool gun for thicker sections. It needs clean material and argon shielding. For a custom aluminum part, spec TIG unless the section is heavy, and confirm the shop welds aluminum to CSA W47.2 if the job is structural.
Do I need CWB-certified welding?
For most structural and load-bearing work in Canada, yes. CWB certification to CSA W47.1 is commonly required on structural steel, and W47.2 on aluminum. Tell us if your job needs it and we route only to certified shops.
Can one shop do both MIG and TIG?
Most full-service fab shops run both and pick per joint. The question to ask is not "do you TIG," it is "have you welded my alloy, to my certification, at my thickness." Send the drawing and the answer sorts itself out.
Last reviewed: July 2026. Related reading: laser vs plasma vs waterjet cutting and powder coat vs paint.
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