MIG vs TIG vs Stick Welding — Full Comparison Guide

Choosing between MIG welding, TIG welding, and Stick welding is one of the most fundamental decisions a welder, fabricator, or welding engineer faces. Each process — formally known as GMAW (Gas Metal Arc Welding), GTAW (Gas Tungsten Arc Welding), and SMAW (Shielded Metal Arc Welding) respectively — has a distinct operating principle, equipment requirement, skill threshold, and range of ideal applications. Understanding these differences in depth is essential whether you are selecting a process for a production line, specifying a Welding Procedure Specification (WPS), or choosing your first welding machine.

This guide compares MIG vs TIG vs Stick welding across every dimension that matters: how each process works, equipment and consumables, weld quality, deposition rate, positional capability, material suitability, cost of ownership, and the practical scenarios where each process wins. Internal code and standard references are provided throughout for ASME Section IX and AWS D1.1 contexts.

Figure 1 — MIG (GMAW) welding process: continuous wire electrode, shielding gas envelope, and arc create the weld pool.

How Each Process Works

MIG Welding (GMAW — Gas Metal Arc Welding)

MIG welding uses a continuously fed solid wire electrode that acts simultaneously as the electrode and the filler material. An arc forms between the wire tip and the base metal, melting both to form the weld pool. An externally supplied shielding gas — typically CO₂, Argon, or blended gases such as 75% Ar / 25% CO₂ (C25) — flows through the welding gun to displace atmospheric oxygen and nitrogen from the arc zone.

The wire feed speed controls amperage, and voltage is set separately on the machine. Skilled MIG welders learn to “read” the arc sound — a steady crackle indicates correct parameters. The process operates in three main metal transfer modes: short-circuit transfer (low heat, thin material), globular transfer (intermediate, generally avoided), and spray transfer (high deposition, flat/horizontal positions). Pulse MIG adds a fourth mode combining spray transfer quality with reduced heat input.

TIG Welding (GTAW — Gas Tungsten Arc Welding)

TIG welding uses a non-consumable tungsten electrode to create the arc. The welder holds the TIG torch in one hand and feeds filler rod manually with the other, while a foot pedal (or thumb control) modulates amperage in real time. Pure Argon is the standard shielding gas for most materials; Argon/Helium mixes increase heat input and penetration for thicker sections and aluminium.

The tungsten electrode does not melt into the weld — it merely sustains the arc. Filler wire selections mirror the base metal chemistry: ER308L for 304 stainless, ER316L for 316 stainless, ER70S-2 for carbon steel, and so on. Autogenous TIG (no filler added) is used on thin-gauge butt joints where fit-up is precise enough that the base metal itself provides sufficient fill. Orbital TIG — mechanised GTAW — is widely used on tube-to-tube and tube-to-header joints in power generation and pharmaceutical piping.

Figure 2 — TIG (GTAW) welding: non-consumable tungsten electrode sustains the arc while the welder feeds filler rod manually, delivering maximum precision and weld quality.

Stick Welding (SMAW — Shielded Metal Arc Welding)

Stick welding is the simplest and oldest of the three processes. A coated electrode — a steel or alloy core rod wrapped in a flux compound — is clamped in an electrode holder. When the electrode tip touches the workpiece and is withdrawn slightly, an arc forms. The arc melts the core rod (which becomes filler metal) and the flux coating simultaneously. The burning flux generates a shielding gas cloud and deposits a slag layer over the molten pool to protect it during solidification.

After each electrode is consumed, the welder stops, removes the stub, chisels off the slag, and inserts a new electrode. This interruption reduces arc-on time but also gives the welder a natural inspection opportunity between passes. Because all shielding is self-contained within the electrode, Stick is independent of any external gas supply — making it ideal for site work, pipeline field joints, and maintenance in remote or exposed locations.

Figure 3 — Stick (SMAW) welding: flux-coated electrode generates its own shielding gas and slag blanket — no external gas supply required.

Equipment and Consumables

Head-to-Head Comparison Table

Weld Quality and Metallurgical Considerations

Heat Input and Heat-Affected Zone

Heat input directly affects the heat-affected zone (HAZ) width, grain growth, and mechanical properties adjacent to the weld. TIG welding inherently produces lower heat input at a given amperage compared to MIG or Stick because of its concentrated arc and precise amperage control. For heat-sensitive alloys such as duplex stainless steels or P91 creep-resistant steel, controlling heat input per the WPS is critical to maintaining the required microstructure and avoiding sensitisation.

MIG welding with spray transfer produces higher heat input per unit length than short-circuit transfer, making transfer mode selection an important part of WPS development. Stick welding heat input is controlled by electrode classification, diameter, and travel speed — all listed in the qualified WPS range.

Delta Ferrite in Stainless Steel Welds

For austenitic stainless steel welding with any process, delta ferrite content in the weld deposit is an essential quality parameter. A ferrite number (FN) of 3–8 FN is typically specified to prevent hot cracking. TIG welding — especially autogenous TIG — is more prone to fully austenitic weld pools with low delta ferrite, making filler selection and dilution control more critical than with MIG or Stick.

Porosity and Contamination

MIG and TIG processes are more susceptible to porosity from shielding gas disruption, moisture on the base metal, or surface contamination than Stick welding, where the flux-generated slag provides a more robust protection mechanism. Pre-weld cleaning — degreasing with acetone or MEK, wire brushing, and grinding of mill scale — is essential for all three processes, but is most critical for TIG.

Material and Thickness Suitability

Welding Positions

All three processes can weld in multiple positions, but each has different position constraints that affect welding position qualification under ASME Section IX or AWS D1.1.

• TIG (GTAW): Capable of all positions (1G through 6G) because the welder has full control of the arc and weld pool size through the foot pedal. 6G pipe qualification with GTAW is widely used as a single qualification covering multiple positions.
• Stick (SMAW): Fully positional — all positions achievable. Electrode selection matters: E6010 and E7018 are designed for vertical and overhead; E6013 is primarily flat/horizontal.
• MIG (GMAW): Short-circuit transfer works in all positions. Spray transfer is limited to flat (1G) and horizontal (2F/2G) because the fluid weld pool cannot be controlled overhead or vertically in spray mode. Pulse MIG bridges this gap by enabling controlled spray-quality deposits in all positions.

Productivity and Cost of Ownership

Deposition Efficiency

Deposition efficiency — the ratio of wire/electrode deposited to that consumed — varies significantly across processes. MIG wire deposition efficiency is approximately 92–98% (minor losses to spatter). Stick electrode deposition efficiency is only 55–70% because the flux coating contributes to slag weight, not deposited weld metal. TIG is close to 100% deposition efficiency for the filler rod consumed, but the slow feed rate means overall metal deposition per hour remains the lowest.

For high-volume structural fabrication where fillet weld consumable quantities and V-groove consumable calculations must be optimised for cost, MIG is typically the most economical process. Stick becomes competitive where gas cylinders, hoses, and feeder capital costs are avoided — particularly on smaller jobs and site work.

Equipment and Running Costs

Industry Applications

Where MIG (GMAW) is Used

MIG welding dominates in automotive manufacturing, general structural fabrication, ship construction, and light to medium industrial fabrication where high throughput is prioritised. Robotic MIG welding cells in automotive plants achieve arc-on times exceeding 90%. In the pressure vessel and tank fabrication industry, MIG is standard for carbon steel plates and shell courses where radiographic quality is achieved through proper WPS control, joint preparation, and run-sequence discipline.

Where TIG (GTAW) is Used

TIG welding is specified wherever weld quality, cleanliness, and metallurgical precision are paramount. Key applications include nuclear and pharmaceutical piping, aerospace structural components, food and beverage stainless equipment, instrumentation tubing, and root passes on critical pipe welds. Orbital GTAW machines are used for unattended, fully repeatable tube welds in semiconductor and biopharmaceutical plants.

In the power generation sector, P91 piping — covered in detail in the WeldFabWorld guide on P91 welding requirements — requires TIG root with carefully controlled heat input and inter-pass temperature. Likewise, tube-to-tubesheet joints in heat exchangers are almost universally qualified as TIG-only welds.

Where Stick (SMAW) is Used

Stick remains the process of choice for pipeline field girth welds, structural repair and maintenance, remote site construction, bridge fabrication, and anywhere that portability and resistance to wind contamination are required. In the oil and gas sector, Stick is used with E6010 (DC+, cellulosic, excellent penetration) for the hot and fill passes on downhill pipeline joints. For low-hydrogen applications such as high-strength or alloy steel, E7018 (iron powder, low hydrogen) is the standard choice under AWS D1.1 and similar structural codes.

In sour service environments governed by NACE MR0175/ISO 15156, electrode selection and hardness control are critical — low-hydrogen electrodes with controlled carbon equivalent are mandatory.

Process Selection Decision Guide

Common Defects and How to Avoid Them

MIG Welding Defects

• Porosity: Usually caused by gas contamination, surface oil, or wind. Increase gas flow rate (15–20 L/min), clean the joint, and shield from drafts.
• Lack of fusion: Travel speed too fast or voltage too low. Increase voltage and slow travel speed, especially at joint root.
• Undercut: Voltage too high or incorrect electrode angle. Reduce voltage and hold a consistent 5–15° drag angle.
• Burn-through: Excessive heat on thin material. Use short-circuit transfer mode, reduce wire feed speed, and increase travel speed.

TIG Welding Defects

• Tungsten inclusion: Caused by touching the tungsten to the weld pool. Maintain clearance; re-grind the tungsten if contaminated.
• Lack of fusion at root: Insufficient amperage or travel speed too fast. Use foot pedal to boost amps at the root, especially on cold starts.
• Oxidation (blue/purple discolouration on stainless): Inadequate Argon purge or back-purging. Increase purge flow and confirm oxygen content is below 50 ppm.
• Cratering cracks: Abrupt arc termination. Always use slope-out (post-flow) to taper the current down at weld termination.

Stick Welding Defects

• Slag inclusion: Incomplete slag removal between passes. Chip thoroughly with a chipping hammer and wire brush before each pass.
• Porosity (hydrogen-induced): Moisture in the flux coating (E7018). Store low-hydrogen electrodes in an oven at 120–150°C per AWS D1.1 Table 4.5.
• Arc blow: DC current magnetises the work and deflects the arc. Switch to AC, re-position the work clamp, or weld toward the clamp.

Certification and Qualification

Welder qualification under ASME Section IX or AWS D1.1 is process-specific. A welder qualified with SMAW is not automatically qualified for GMAW or GTAW — each process requires its own performance qualification test (WPQ). Similarly, a WPS qualified for SMAW cannot be used for GTAW without a separate PQR unless the engineering document specifically allows a combination.

ASME Section IX QW-402 through QW-410 define essential and supplementary essential variables that — if changed beyond qualified limits — require re-qualification. For process-specific variable review, see the WeldFabWorld P-Number and F-Number guide and the ASME Section IX practice quiz.

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© WeldFabWorld.com — Technical content for welding engineers, inspectors, and fabricators. All process parameters are indicative; always follow qualified WPS documentation and applicable codes.