MIG, TIG or Stick: Which Weld Your Job Needs

Guide

Welding is not one process. The three in common use produce joints that differ in strength, appearance, cost and where they can be done. Specifying the wrong one usually shows up either in the finish or in the invoice.

MIG — the workhorse

A wire feeds continuously through the torch while shielding gas protects the pool. Because the wire feeds automatically, deposition is fast and the process is easy to learn relative to the others.

• Best for production work, structural fabrication, thicker sections, long runs of weld.
• Fast — the highest deposition rate of the three, which makes it the cheapest per metre.
• Appearance — good but not exceptional. Adequate where welds are ground, coated or hidden.
• Limits — the shielding gas blows away in wind, so it is awkward outdoors without screening. Less controllable on very thin material.

TIG — the finish process

A non-consumable tungsten electrode strikes the arc and filler is fed in by hand, so the welder controls heat and filler independently. It is slow and demands real skill.

• Best for visible architectural work, thin material, stainless steel, aluminum, and anything where the weld is part of the finished appearance.
• Appearance — the cleanest weld available. On polished stainless handrail joints, a good TIG weld dressed and polished becomes almost invisible.
• Control — very low heat input, so thin tube does not burn through and distortion stays minimal.
• Limits — slow, therefore expensive. Needs very clean material; contamination shows immediately.

This is why the same handrail may be MIG welded in its hidden structure and TIG welded at every visible joint. It is not inconsistency, it is the right process in each place.

Stick — the site process

A flux-coated electrode provides both filler and shielding as it burns. No gas bottle is needed, which is the whole point.

• Best for site work, outdoors, in wind, on painted or slightly rusty steel, and in awkward positions.
• Portable — the equipment is simple and tolerant of poor conditions.
• Limits — slag must be chipped off between passes, the finish is the roughest of the three, and it is unsuitable for thin material.

Matching process to material

Mild steel takes all three; the choice is decided by speed, location and finish. Stainless steel is usually TIG where it is visible, MIG where it is not, and needs care to avoid the discolouration that appears as a rainbow tint at the heat-affected zone. That tint is not just cosmetic — it indicates the protective oxide layer has been damaged, and it needs pickling or passivation afterwards or it will corrode there first.

Aluminum is the demanding one. It conducts heat away fast, forms a tough oxide skin, and gives little visual warning before it collapses. It needs AC TIG or specialised MIG, and it is not a job for a general steel welder.

What distortion means for your part

Every weld shrinks as it cools, and shrinkage pulls the parts. On a long handrail or a large frame, uncontrolled welding sequence produces a bow you cannot straighten out afterwards. Controlling it is a fabrication skill: tacking in sequence, alternating sides, using jigs, and sometimes deliberately pre-setting the part in the opposite direction. It is a good question to ask on any long or precise assembly.

Questions worth asking a fabricator

• Which process will be used on the visible joints, and will they be dressed and polished?
• Are welders qualified for the material and positions involved?
• Will stainless welds be pickled or passivated after welding?
• How will distortion be controlled on the long members?
• What is welded in the shop and what is welded on site?

See our welding page, or choosing the right metal if the material is still open.