Choosing the Right Welding Gas
Welding gas is the one consumable that changes everything about a weld: penetration, spatter, strength and finish. Yet it is often bought on habit rather than matched to the job. This guide explains what welding gas actually does, the handful of gases Australian workshops rely on, and which gas suits each process and metal, whether that is MIG on mild steel, TIG on stainless, or oxy-acetylene work on site. For deep dives into individual processes there are dedicated guides linked throughout; this page is the place to start when deciding what should be in the bottle.
What Welding Gas Does
Welding gases fall into two groups that do very different jobs.
Shielding gases protect the weld. Molten metal reacts instantly with the oxygen and nitrogen in air, and a contaminated weld pool means porosity, brittleness and failure. In MIG and TIG welding, gas flows from the torch nozzle and blankets the weld pool until it solidifies. The choice of shielding gas also shapes the arc, changing how deep the weld penetrates and how clean it looks.
Fuel gases make the heat. In oxy-acetylene welding, cutting and brazing, acetylene burns with oxygen to produce the flame that does the work. Here the gas is not shielding the weld; it is the energy source itself.
The Main Welding Gases
Four gases cover almost all welding done in Australian workshops.
Argon is the universal shielding gas: fully inert, heavier than air, and the base of nearly every mix. It is used pure for TIG welding and for MIG welding aluminium, and blended for steel. The guide to argon in welding processes covers it in depth.
Argon/CO2 mixes are the standard shielding gases for steel. Pacshield 80/20 (80% argon, 20% CO2) is the all-round workshop mix for mild steel MIG welding, while Pacshield 5/2 (92% argon, 5% CO2, 2% oxygen) gives a finer arc and cleaner finish for thin sheet and automotive panels.
Carbon dioxide used straight is an economical option for mild steel MIG where deep penetration matters more than spatter and cleanup.
Oxygen and acetylene are the fuel-gas pair for oxy-acetylene welding, cutting, heating and brazing, still the most portable way to cut and join steel without power.
Welding Gas by Process
MIG Welding
MIG uses argon/CO2 mixes on steel, with Pacshield 80/20 as the general-purpose choice and Pacshield 5/2 for thinner or finish-critical work, and pure argon on aluminium. Flow rates, cylinder run times and gas choice by metal are covered in the full guide to MIG welding gas.
TIG Welding
TIG welding runs on pure argon for nearly everything: mild steel, stainless steel and aluminium alike. TIG puts a premium on arc stability and cleanliness, and argon delivers both. Argon/CO2 mixes must not be used for TIG, because CO2 breaks down in the arc and contaminates the tungsten electrode.
Flux Core Welding
Self-shielded flux core wire generates its own shielding from the flux inside the wire, so it needs no gas bottle at all, which is why it suits outdoor and windy conditions. Gas-shielded flux core wire, used for higher deposition rates in fabrication, typically runs on Pacshield 80/20, the same mix as general MIG work.
Oxy-Acetylene Welding and Cutting
Oxy work needs two cylinders: oxygen and acetylene. The pairing produces the hottest practical fuel-gas flame, hot enough to weld, braze, heat and cut steel with no electricity, which keeps it a staple for site work, rural repairs and heavy maintenance. The guide to oxy-acetylene welding covers flame settings and technique.
Choosing Welding Gas by Metal
For mild steel, run Pacshield 80/20 for MIG, pure argon for TIG, or straight CO2 for MIG where penetration outranks finish.
For stainless steel, run TIG on pure argon. Keep high-CO2 mixes away from stainless, as excess carbon pickup can compromise its corrosion resistance.
For aluminium, the answer is pure argon for both MIG and TIG. Aluminium’s oxide layer and heat conductivity demand a fully inert shield; the guide to argon for aluminium welding explains the details.
Welding Gas FAQ
What welding gas should a general workshop keep on hand?
For a workshop MIG welding mild steel, one bottle of Pacshield 80/20 covers most work. Add pure argon if TIG or aluminium jobs come through the door, and an oxygen and acetylene pair if cutting and brazing are part of the workload.
Can you weld without gas?
Only with self-shielded flux core wire, which makes its own shielding. Standard MIG wire without gas produces porous, brittle welds, and TIG always needs argon.
Is welding gas the same as the gas used for cutting?
No. MIG and TIG use shielding gases such as argon and argon/CO2 mixes, which protect the weld but do not burn. Cutting and brazing with an oxy set use oxygen and acetylene, which produce the flame itself.
What size welding gas cylinder is best?
It depends on usage: D size for occasional repairs, E size for regular workshop welding, G size for daily fabrication. The guide to choosing the right gas cylinder size works through run times and the trade-offs.
Welding Gas Supply from Pacific Gas
Pacific Gas supplies the full welding gas range, argon, Pacshield 80/20, Pacshield 5/2, carbon dioxide, oxygen and acetylene, in D, E and G cylinders through local distributors across Australia. Supply works on cylinder exchange, swapping an empty bottle for a full one the way a BBQ bottle is swapped, on customer-owned cylinders with no rental contract. To stock the right gas for the work, find a distributor nearby or contact Pacific Gas for advice.
