Arc Welding Processes Explained: MIG, TIG, Stick & PAW Guide

What Is Arc Welding?

Arc welding is a fusion welding process that uses an electric arc to generate heat to melt and join metal. An electric current passes between an electrode and the workpiece, and the intense heat of the arc, reaching temperatures well over 3,000°C, melts the base metal (and often a filler material) to form the weld.

To supply the electrical energy for this, arc welding equipment uses one of two types of power supply:

• Constant current (CC) power supplies hold the current relatively steady, even as the voltage fluctuates. These are best suited to manual welding processes like Stick (SMAW) and TIG (GTAW), where it's difficult for an operator to hold a perfectly steady arc length, so the voltage naturally varies as the hand moves.
• Constant voltage (CV) power supplies hold the voltage steady and let the current vary instead. These are typically used for automated or semi-automated processes like MIG (GMAW), flux-cored (FCAW) and submerged arc welding (SAW), where a continuously fed wire electrode needs consistent voltage to maintain a stable arc.

Understanding this distinction matters because it explains why certain machines and processes pair together. You can't simply swap a CC power source onto a wire-feed MIG setup and expect the same results.

A note on safety: the intense heat, UV radiation and welding fumes produced by an electric arc mean proper PPE (welding helmet, gloves, protective clothing) and fume extraction are essential for every arc welding process. For a full breakdown of fume risks and compliance requirements, see our Welding Fume Extraction Guide.

A Brief History of Arc Welding

Arc welding's roots go back to the 1880s, when the discovery that an electric arc could generate enough heat to melt metal led to the first carbon arc welding methods. This laid the groundwork for shielded metal arc welding (SMAW), commonly known as Stick welding, which became the dominant welding process for most of the 20th century thanks to its simplicity and low equipment cost.

As industry demanded faster, cleaner and more automatable methods, new processes followed:

Today, these processes sit alongside each other in industry, each suited to different materials, thicknesses and production demands. Which is exactly why understanding how they compare matters before choosing equipment.

Where Is Arc Welding Used?

Arc welding processes are used across almost every sector of metal fabrication and manufacturing, including:

• Structural steel and construction: Stick and MIG welding are widely used on-site and in structural fabrication for their portability and speed
• Shipbuilding: SAW and MIG are common for the long, heavy welds involved in hull and structural sections
• Automotive manufacturing: MIG welding is a mainstay of automotive production lines, with TIG and PAW used for higher-precision applications like exhaust components and body panels
• Pressure vessels and pipelines: TIG and SAW are favoured where weld quality and integrity are critical
• Aerospace and medical device manufacturing: TIG and PAW are used for their precision on thin, high-value materials
• Maintenance, repair and general fabrication: Stick welding remains popular for its simplicity, portability and tolerance of less-than-ideal working conditions

Because each process brings different strengths, most fabrication shops use a combination of processes rather than relying on just one. Which is where understanding the differences between them becomes genuinely useful.

The Main Arc Welding Processes: MIG vs TIG vs Stick

The three most common arc welding processes: MIG, TIG and Stick, all use an electric arc to join metal, but differ significantly in equipment, skill level, speed and finish quality.

Stick Welding (SMAW)

Also known as shielded metal arc welding (SMAW) or manual metal arc welding (MMA), Stick welding uses a flux-covered consumable electrode rod. An electric current strikes an arc between this rod and the base metal; as the rod melts, its flux coating produces a shielding gas and forms a protective layer of slag over the weld.

• Advantages: simple, portable, inexpensive equipment; tolerant of wind, rust and less-than-ideal surface conditions; minimal operator training required
• Considerations: slower than wire-fed processes since electrodes need frequent replacement; slag must be chipped away after welding; generally a rougher finish than MIG or TIG
• Best for: site work, structural steel, maintenance and repair, outdoor conditions

MIG Welding (GMAW)

Gas metal arc welding (GMAW), commonly called MIG (Metal Inert Gas), uses a continuously fed wire electrode that acts as both the arc conductor and the filler material, shielded by an externally supplied gas. It's typically run on a constant voltage, direct current power source.

MIG welding has four main methods of metal transfer: globular, short-circuiting, spray and pulsed-spray, each suited to different material thicknesses and finish requirements. Spray transfer, for example, gives a high-quality, near-spatter-free finish and works well on stainless steel and aluminium. While short-circuit transfer suits thinner materials but isn't recommended for thicker sections due to lower arc energy.

• Advantages: fast welding speed, continuously fed wire reduces downtime, relatively easy to learn, good for high-volume production
• Considerations: more complex equipment than Stick; less portable; generally needs a cleaner environment and shielding gas supply
• Best for: production welding, automotive manufacturing, general fabrication on steel and aluminium

TIG Welding (GTAW)

Gas tungsten arc welding (GTAW), or TIG (Tungsten Inert Gas), uses a non-consumable tungsten electrode to create the arc, with a separate filler rod added by hand where needed. An inert shielding gas (typically argon) protects the weld pool from contamination.

TIG offers the highest level of control and precision of the three processes, making it the preferred choice where weld appearance and quality are critical. For a full breakdown of TIG welding, including strength on thick steel, common mistakes and safety considerations, see our General TIG Welding Guide.

• Advantages: clean, high-quality, precise welds; excellent control over heat input; suited to thin materials and non-ferrous metals like aluminium and stainless steel
• Considerations: slower than MIG or Stick; requires greater operator skill; typically more expensive equipment
• Best for: precision work, aerospace, pressure vessels, thin materials, applications where weld appearance matters

Which Process Suits Which Material?

For a deeper look at aluminium-specific process choices, see our Aluminium Welding Guide.

Once you've settled on the right process for your job, the next step is choosing the right machine. Our full guide on how to choose the right welding machine walks through duty cycle, power supply and portability considerations in more detail.

Plasma Arc Welding (PAW) Process

Plasma arc welding (PAW) is an advanced arc welding process closely related to TIG. The key difference is that in PAW, the tungsten electrode sits in the body of the torch, allowing the plasma arc to be separated from the shielding gas envelope. The plasma is then forced through a fine-bore copper nozzle, which constricts the arc so it exits at high velocity (approaching the speed of sound) and at temperatures approaching 20,000°C.

This constriction gives PAW a more concentrated, stable arc than TIG, with several practical benefits:

• Greater precision and control, particularly valuable for high-integrity applications in aerospace, medical device and electronics manufacturing
• Keyhole-mode welding, allowing full-penetration welds in relatively thick material in a single pass
• Better tolerance of joint misalignment than laser beam welding (LBW), while offering better penetration than standard TIG
• Faster welding speeds than TIG in many applications, often at a lower cost than laser beam welding

PAW can join all the same metals as TIG, including aluminium, copper, steel and stainless steel. It’s commonly used in automotive manufacturing for body panels and exhaust system components, alongside its established role in aerospace and medical applications.

The trade-off is complexity: PAW requires more expensive equipment than TIG, more careful torch maintenance, and a higher level of operator skill, since the process is less tolerant of variations in fit-up and setup.

FAQs

What is the energy used to strike an arc called?

Voltage. A sufficiently high voltage is needed to overcome the resistance of the air gap between the electrode and the workpiece, ionising the air and creating a conductive path for the arc.

What's the difference between MIG, TIG and Stick welding?

MIG uses a continuously fed wire electrode and shielding gas for fast, production-friendly welding. TIG uses a non-consumable tungsten electrode and a separate filler rod for precise, high-quality welds. Stick uses a flux-covered consumable electrode rod, making it simple, portable and tolerant of harsher conditions, but slower and less refined in finish.

What is Plasma Arc Welding used for?

PAW is typically used where precision and weld quality are critical, such as aerospace components, medical devices, and automotive applications like exhaust systems and body panels. It offers greater arc concentration and control than standard TIG welding.

Which arc welding process is easiest to learn?

Stick welding generally requires the least operator training, making it a common starting point. MIG is also relatively accessible, while TIG demands the most skill and practice to master.

Can arc welding be used on aluminium?

Yes. TIG welding is the most common choice for aluminium, offering excellent control, with specialist MIG setups also used for thicker aluminium sections. See our Aluminium Welding Guide for full details.

When was arc welding invented?

The earliest arc welding methods date back to the 1880s. From there, the process family expanded significantly through the 20th century; Stick welding (SMAW) became dominant for decades, followed by submerged arc welding in the 1930s, TIG and MIG in the 1940s, and Plasma Arc Welding in the late 1950s.