Electric arc welding uses an electrical current to melt metal and join pieces together

Electric arc welding is a process where an electric current jumps across a gap between two pieces of metal, creating intense heat that melts the metal so it can fuse together. The "arc" is that electrical spark — it reaches temperatures around 6,500 degrees Fahrenheit, hot enough to melt steel. A welder guides a metal rod (called an electrode) along the joint where two pieces of metal meet, and the arc melts both the rod and the metal underneath, creating a bond as the molten metal cools and hardens.

This is different from other joining methods like bolting or riveting because the metal pieces actually become one continuous piece rather than being held together by fasteners. The result is stronger than the original metal in many cases, which is why arc welding is used in construction, shipbuilding, automotive repair, and anywhere metal structures need to hold under stress.

Key Takeaways

  • An electric arc creates heat by jumping across a gap between metal pieces, melting them so they can fuse into a single joint.
  • The three main types of electric arc welding — stick, MIG, and TIG — differ in how the electrode is fed and what gas protects the weld.
  • Arc welding requires safety gear including a helmet with a dark lens, gloves, and protective clothing because the arc produces ultraviolet light and sparks.
  • The strength of an arc weld depends on the welder's skill, the type of metal being joined, and whether the joint is cleaned properly before welding.

The three main types of electric arc welding

Stick welding (also called shielded metal arc welding or SMAW) is the oldest and most portable type. The electrode is a metal rod coated in flux — a chemical compound that burns away and creates a gas shield around the weld to keep oxygen out. The welder holds the electrode in a clamp and manually moves it along the joint, striking an arc and maintaining the right distance as the rod burns down. Stick welding works outdoors and in windy conditions because the flux creates its own protection, but it leaves slag (a crusty residue) that must be chipped away after each pass.

MIG welding (metal inert gas, also called GMAW) feeds a thin wire electrode continuously through a gun, like a spool. The welder pulls the trigger and the wire feeds automatically while an external gas — usually argon or a mix of argon and carbon dioxide — flows around the arc to shield it. MIG is faster and cleaner than stick welding because there is no slag, and it is easier to learn. It works best indoors or in protected spaces because wind can blow away the shielding gas.

TIG welding (tungsten inert gas, also called GTAW) uses a non-consumable tungsten electrode that does not burn away. The welder holds the torch in one hand and feeds a separate metal rod into the arc with the other hand, similar to how a plumber might solder copper pipe. TIG produces the highest quality welds and works on almost any metal, but it is the slowest and requires the most skill. Like MIG, it needs an external gas shield and works best indoors.

What happens during the welding process

When the electrode touches the metal or comes very close to it, electrical resistance causes the temperature to spike instantly, creating the arc. The arc is not a continuous flame — it is a stream of electrons jumping across the gap, and that movement generates the heat. As the electrode melts, it becomes filler material that flows into the joint. At the same time, the base metal (the pieces being joined) also melts, and the two molten pools mix together.

The shielding gas or flux keeps oxygen and nitrogen from the air from mixing with the molten metal. If oxygen gets into the weld, it creates brittle spots and weakens the joint. As the welder moves the electrode along, the molten metal cools behind it and solidifies into a bead — the visible line of metal that holds the pieces together. A good bead is smooth and consistent; a poor one may have gaps, cracks, or weak spots where the metal did not fuse properly.

Safety gear and hazards

The arc produces ultraviolet and infrared light intense enough to cause arc eye — a painful burn to the cornea that can happen in seconds without protection. A welding helmet with a dark lens (usually shade 10 or higher) is essential and must cover the entire face. The lens darkens automatically when the arc strikes, so the welder can see the joint clearly without lifting the helmet.

Sparks and molten metal splash can travel several feet, so welders wear heavy leather or flame-resistant gloves, a leather apron or jacket, and closed-toe boots. Long sleeves and long pants are standard. The work area should be clear of flammable materials because sparks can ignite paper, cloth, or fuel. Welding also produces fumes — especially when welding galvanized steel or painted metal — so good ventilation or a fume extractor is necessary to avoid inhaling zinc oxide or other harmful compounds.

Why metal type and joint preparation matter

Different metals require different electrodes and techniques. Steel is the most common and forgiving. Aluminum melts at a lower temperature and conducts heat differently, so it usually requires MIG or TIG welding with special electrodes. Stainless steel needs specific filler material to maintain its corrosion resistance. Mixing the wrong electrode with the wrong base metal can result in a weld that looks fine but fails under stress.

Before welding, the joint must be clean. Rust, paint, oil, and dirt create weak spots in the weld because they prevent the base metal from melting and fusing properly. Welders use wire brushes, grinders, or solvents to clean the area. The gap between the pieces also matters — if it is too wide, the filler material will sag and create a weak joint; if it is too tight, the heat may not penetrate all the way through. Proper fit-up and clamping before striking the arc saves time and produces stronger results.

Where arc welding is used

Structural steel for buildings and bridges relies almost entirely on arc welding because it creates joints as strong as the surrounding metal. Shipbuilding uses arc welding for hulls and internal structures. Automotive shops use it for frame repair and custom fabrication. Pipeline construction, heavy equipment manufacturing, and pressure vessel fabrication all depend on arc welding because the joints must withstand high stress or pressure.

Smaller applications include farm equipment repair, gate and fence building, and artistic metal sculpture. Any situation where two pieces of metal need to become one permanent structure is a potential use for arc welding. The choice of which type — stick, MIG, or TIG — depends on the metal, the location, the required quality, and how fast the work needs to be done.

Frequently Asked Questions

Can you arc weld outdoors?

Stick welding works outdoors because the flux creates its own gas shield. MIG and TIG welding require external shielding gas, which wind can blow away, making them difficult outdoors. If you must use MIG or TIG outside, you need a windbreak or a tent around the work area.

How hot does an arc get?

The arc itself reaches around 6,500 degrees Fahrenheit, though the exact temperature varies by welding type and current. The base metal melts at a lower temperature — steel melts around 2,800 degrees — so the arc is more than hot enough to fuse it.

What is the difference between arc welding and soldering?

Arc welding melts the base metal itself and creates a joint as strong as the surrounding metal. Soldering uses a separate filler metal with a much lower melting point and does not melt the base metal, so the joint is weaker. Arc welding is for structural strength; soldering is for electrical connections or light-duty joints.

Do you need a license to arc weld?

Most states do not require a license to weld, but many employers and industries do require certification. Certification means passing a test that proves you can produce welds that meet specific standards. Some states require certification for welders working on pressure vessels or pipelines.

How long does it take to learn arc welding?

Basic stick welding skills can be learned in a few weeks of practice, but becoming proficient enough to pass certification tests usually takes several months of hands-on training. TIG welding takes longer to master because both hands and a foot pedal must work together.