Posted by Gary Fahey on

MIG Welding:

Also known as Gas Metal Arc Welding (GMAW), it involves a welding gun that continuously feeds a consumable wire electrode through the torch, which acts as both the electrode and filler material. It’s commonly used with a shielding gas like argon or CO2 mixtures.

TIG Welding:

Also called Gas Tungsten Arc Welding (GTAW), it uses a non-consumable tungsten electrode to create the arc, with filler material added separately by hand if needed. It typically requires a shielding gas like argon or helium.

MIG and TIG are both arc-welding processes, but they trade speed for finesse.

 

Key Differences – Here’s a comparison table for clarity:

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Welding Process Comparison
MIG (GMAW) vs. TIG (GTAW) Welding Comparison
Aspect MIG (GMAW) TIG (GTAW)
Electrode Continuously fed consumable wire Non-consumable tungsten
Filler metal The wire itself (auto-fed) Optional, added by hand as rod
Shielding gas Usually 75/25 Ar/CO₂ for steel; pure Ar for aluminum/stainless Almost always pure argon (sometimes He mixes)
Polarity (1) DCEP for steel; AC for aluminum with a spool gun DCEN for steel/stainless; AC with balance control for aluminum/magnesium
Speed & ease Fast, easier to learn; great for production Slower, harder to master; precise control
Thickness sweet spot Medium to thick materials; good for long beads Thin to medium; excellent for very thin sheet
Appearance Decent, sometimes spatter to clean Very clean, precise, “stack-of-dimes”
Typical uses Fabrication, automotive frames, gates, general repair Stainless & aluminum fab, food-grade tubing, bikes, art, precision parts
Wind sensitivity More tolerant (still needs shielding) Very sensitive; indoor or well-shielded only
Equipment cost Lower to mid Higher (foot pedal, high-freq start, AC balance for Al)

Choose Which Type of Weld

  • Choose MIG if you want speed and ease for general fabrication—mild steel frames, trailers, brackets, thicker stock (≥1/8″ / 3 mm), or when you’ve got lots of long welds to lay down.
  • Choose TIG when appearance, precision, or thin materials matter—stainless tanks, motorcycle exhausts, aluminum parts, or anything where heat input must be tightly controlled.

 

Notes:

  • Aluminum: MIG works with a spool gun (fast but less pretty). TIG on AC gives the cleanest results and best control.
  • Stainless: Both work; TIG shines for neat, low-heat-tint welds (often with back-purge on tubing).
  • Thin sheet (<1/16″ / 1.6 mm): TIG is safer—less risk of burn-through.
  • Outdoors: Flux-cored MIG (FCAW) beats both solid-wire MIG and TIG for wind tolerance.

 

 

Glossary

(1)
DCEN (Direct Current Electrode Negative): This is a welding polarity where the electrode (tungsten) is connected to the negative terminal, and the workpiece is positive. It provides deep penetration and a narrow weld bead because most of the heat is concentrated on the workpiece. It’s ideal for welding ferrous metals like steel and stainless steel, as these materials don’t form heavy oxide layers that need aggressive cleaning.

AC (Alternating Current) with Balance Control: AC switches between positive and negative polarity rapidly. This helps break up and clean surface oxides (like the aluminum oxide layer) during the electrode-positive half-cycle, while providing penetration during the electrode-negative half-cycle. Balance control is a feature on some welding machines that lets you adjust the percentage of time spent in each half-cycle (e.g., more electrode-negative for better penetration, or more electrode-positive for stronger cleaning). It’s commonly used for non-ferrous metals like aluminum and magnesium, which have oxide layers that must be removed for a clean weld.

Example for specific metals
• Steel and Stainless Steel: These are typically welded with DCEN because they require good heat input for penetration without much need for oxide cleaning. Using AC on them could lead to excessive electrode wear or unstable arcs.
• Aluminum and Magnesium: AC is preferred to alternate between cleaning (removing oxides) and welding. Without this, the weld could be contaminated or weak. Balance control fine-tunes the process—for example, 70% electrode-negative for deeper penetration on thicker aluminum, or more balanced for thinner pieces.