MIG vs MAG vs TIG Welding: Which Process Do You Need?

You pull a trigger, the gun spits wire, and fifty seconds later you have a bead that looks like a factory job — on the same bench where your neighbor is coaxing a lazy puddle with a stick of filler rod and a torch that looks like a drinking straw. Both welders think they’re doing the same job. Only one of them is going to make money doing it. The gap between MIG, MAG, and TIG isn’t about talent or price; it’s about physics, shielding gas, and what you actually want the arc to do. This guide breaks down all three so you can stop guessing and start picking the right process for the job in front of you.

MIG, MAG, and TIG: What’s Actually the Difference?

Straight to it: MIG and MAG are the same welding process wearing different gas, and TIG is a fundamentally different process. In MIG and MAG, the arc burns between a continuously fed consumable wire and the workpiece, so one component does two jobs at once: it is the electrode and the filler metal. In TIG (also called GTAW), the arc burns between a non-consumable tungsten electrode and the workpiece, and the filler metal is added by hand from a separate rod. Change where the filler comes from and you change everything downstream: travel speed, puddle control, which metals you can join, and the finish on the seam.

Here is the fast decision rule to keep in your pocket while you read the rest of this guide:

• MIG (inert gas, usually argon blends) — thin material, stainless, aluminum, cleaner beads, and any job where you want more control than a stick electrode gives you.
• MAG (active gas, usually CO₂ or 75/25) — carbon steel, structural work, dirty or rusted steel, production volume, lowest cost per meter of finished weld.
• TIG — thin stainless and aluminum, copper, dissimilar metals, root-plus-cap joints, and any seam that has to look good or stay easy to clean inside.

The three axes that actually separate them

Set the acronyms aside for a minute and look at three mechanical questions. Where does the filler metal come from? What protects the molten weld from the air? Who controls the heat?

Axis	MIG / MAG (GMAW)	TIG (GTAW)
Filler metal	Continuous consumable wire electrode (roughly 0.6–2.4 mm), pushed by a powered wire feeder	Manual filler rod, fed in by the welder’s other hand
Shielding	Inert gas such as argon (MIG) or active gas such as CO2 (MAG)	Almost always pure argon, sometimes argon with helium
Heat control	Constant-voltage machine: wire feed speed sets current, voltage sets arc length	Constant-current machine: amperage plus torch angle set depth and bead shape

AWS organizes all of this in AWS A5.32: gas metal arc welding is process 13, with 131 for MIG and 135 for MAG, while gas tungsten arc welding is process 141. Under European standard EN 14610, the generic term for wire-electrode gas-shielded welding is “gas-shielded metal-arc welding,” also numbered 13 — you can see both naming conventions in the European welding dictionary.

Why Americans say MIG and most of the world says MAG

MIG means metal inert gas. MAG means metal active gas, and “active” simply refers to whether the shielding gas chemically reacts with the weld pool. Both terms describe the same machine and the same consumable wire; the split is largely regional. Pure argon suits aluminum and stainless, but CO₂ is cheaper and gives deeper penetration on carbon steel, so European shops that leaned on CO₂ for steel began saying MAG while American shops kept saying MIG. Neither term is wrong, and most shops mix them freely.

“Gas-shielded arc welding” is the umbrella phrase covering MIG, MAG and TIG, because all three depend on a curtain of gas around the arc rather than a flux coating. That is worth remembering when you shop for cylinders, since the blend matters more than the letters on the machine. Our guide to shielding gas choices breaks down the blends later in this article.

What the numbers mean for your work

On throughput, MIG/MAG wins because the wire feeds continuously and the process can be automated. Fronius points out that MIG/MAG cuts welding time because it can be mechanized, and that the higher travel speed also leaves a smaller heat-affected zone. OpenLearn puts typical MIG/MAG deposition rates at 1.25–7.5 kg/h using power supplies in the 60–500 A, 16–40 V DC band. For rough amperage sizing, Miller’s GMAW guidelines offer a memorable rule of thumb: multiply material thickness in inches by 1,000, so 0.001 in. (0.025 mm) of steel calls for roughly 1 ampere.

Who this guide is for

It works for the weekend hobbyist building a trailer frame in a garage, the farm repair welder wrestling with rusted equipment and bad fit-up, the apprentice trying to understand why wire feed speed matters, and the production fabricator quoting a structural contract. All of them end up asking the same question at the counter: which machine, which gas, which wire.

We use working examples throughout: aluminum MIG welding for the shop that keeps burning through thin panels, aerospace TIG welding for understanding why TIG lives in aerospace, why stick welding still wins for off-site repair work, and a plain look at how shielding gas works before you start shopping cylinders.

How Each Process Works: Wire, Tungsten, Gas, and Arc

Before you pick a process, know what happens between the torch and the metal. MIG, MAG and TIG all create an arc, use a shielding gas and melt the work together. They differ in three ways: where the filler metal comes from, what protects the molten pool, and how heat input is controlled.

MIG/MAG: The Consumable Wire Does Everything

In MIG and MAG the electrode is the filler metal: solid wire feeds through the gun at a controlled rate, and the arc melts the tip as fast as it feeds. One process, two names, and the only real difference is the shielding gas. OpenLearn’s guide to gas-shielded arc welding explains that MIG uses an inert gas (usually argon) and MAG an active gas (usually CO2 or a blend), with everything else identical.

Wire diameters run from about 0.75 mm to 2.25 mm, with 0.8, 0.9, 1.0, 1.2 and 1.6 mm the everyday spool sizes. The wire is usually copper-coated, and that is not cosmetic: copper conducts better than steel, so the coating improves current flow through the feeder liner and reduces hot, wire-sticking guns.

Two power source characteristics define MIG/MAG: direct current electrode positive (DCEP), torch positive and work lead negative, and a constant-voltage characteristic with a flatly falling voltage-current curve. In practice, voltage holds the arc at a set length, while wire feed speed sets the current.

This is where the operating point comes in. The arc and the power source each have a characteristic curve, and where they cross is where the machine settles. Raise the wire feed speed and the point slides along the power source curve, current climbing and voltage falling. Hold the arc length by raising voltage in tandem, which is why Miller’s GMAW guidelines pair the two settings.

TIG: A Non-Consumable Electrode and a Filler Rod You Feed by Hand

TIG works differently. The electrode is tungsten, which is never consumed in a properly executed weld. It is a sharp, heat-resistant pin that focuses the arc. The filler comes from a separate rod you feed into the puddle by hand, deciding when, where and how much goes in.

Manual filler feeding gives you granular heat control: melt a millimetre of base metal, add a short stub of rod, let the puddle freeze, then add more. MIG/MAG cannot do that, because the wire feeds at whatever rate the machine is set to.

TIG power sources use a constant-current characteristic instead: current stays where you set it and the arc length floats within a range, which is why TIG feels controllable on thin material and awkward on thick plate.

Polarity is the other half. Most TIG runs on DC electrode negative (DCEN): the work is positive, the tungsten negative. Two-thirds of the heat lands in the workpiece and one-third goes into the electrode, which is why thin stainless does not cook and a heavily loaded tungsten survives a long bead.

DCEN suits carbon steel, stainless steel, nickel alloys, copper, titanium and zirconium. Aluminum and magnesium differ: their stubborn, refractory oxide layer cannot be broken reliably by a pure DC arc. That is where AC comes in. The positive half-cycle crushes and breaks up the oxide while the negative half-cycle drives penetration into the base metal. Modern TIG machines use a square-wave inverter with a balance control for the mix.

Striking the Arc Without Ruining the Electrode

How the arc starts matters more in TIG than beginners expect. The machine ignites it with a high-frequency generator, a burst of high-voltage AC that jumps the gap without the two ever touching. It is nearly inaudible and leaves the tungsten clean.

The old-school alternative is scraping the tungsten against the work until a spark appears. It works, and it is a bad habit: you grind a nick into the tip, contaminate the electrode with base metal, and drive tungsten inclusions into the weld, where they become cracking and corrosion sites that later grinding will not fix. Modern machines offer a lift-arc mode using a controlled short circuit, a far better third option.

TIG machines also carry a much higher open circuit voltage than MIG/MAG boxes, typically around 80 V, which is why TIG leads and work clamps need good insulation.

Slag-Free Welding: The Underrated Advantage

Both MIG/MAG and TIG are slag-free processes. There is no flux blanket to chip off to reveal the weld, and TIG produces almost no spatter because no consumable wire is being exploded into droplets. MIG/MAG does spatter, especially in short-circuit transfer, where droplets can oxidise and fling off.

Once the physics make sense, the equipment does too. A MIG/MAG gun needs a feeder, a liner and a constant-voltage source to push a consumable electrode. A TIG torch needs a clean, shaped tungsten, a current-controlled source with high-frequency ignition, and a filler rod you feed by hand. Both need gas, and the right shielding gas for each is covered in the Linde guide to shielding gases.

MIG and MAG Deep Dive: Gases, Wires, and the Four Transfer Modes

MIG and MAG are one process wearing two different gas bottles. Everything else is identical: a constant-voltage power source, a continuous consumable wire, and a shielding gas that protects the molten pool from the air while shaping how the arc behaves. Get the gas right and the process rewards you. Get it wrong and you will spend an afternoon blaming your gun, your wire, or your own hands for something the cylinder caused.

Shielding Gas Blends and What They Are For

Shielding gases are blends of argon and carbon dioxide, sometimes with small additions of oxygen or helium. Argon is inert and does not react with the weld pool. Carbon dioxide is active: it slightly oxidises the molten metal, which improves penetration on thicker steel but throws more spatter. More argon means a cleaner, more stable arc and a nicer bead. More CO2 means more bite, more spatter, and a louder, rougher arc.

Blend	Best use
75% argon / 25% CO2 (75/25)	Carbon steel workhorse. Short-circuit mode, thin to medium plate.
90% argon / 10% CO2 (90/10, C-10)	Spray on thicker steel and stainless, less spatter than 75/25.
100% CO2	Heavy carbon steel and thick sections. Penetration over appearance.
Argon with a little oxygen (93/5/2 style)	Stainless and high-speed sheet. Oxygen stabilises the arc and improves wetting.
100% argon or argon-helium	Aluminium and non-ferrous. Helium adds heat for heavier sections.

One of the most useful thresholds in the process comes from the Lincoln Electric MIG troubleshooting guide: axial spray transfer needs CO2 content below roughly 18 percent. At 18 percent you sit right on the practical limit, and beyond that the arc wants to ball up rather than spray. That explains why 82/18 exists as a cylinder and why pure CO2 will never spray.

Blends also behave differently in the mess. Hobart Brothers points out that a 75/25 mix typically gives less consistent transfer and more spatter than 90/10. If your beads are dirty and the gun is bouncing, swapping cylinders is often faster than touching the machine. Linde’s shielding gas overview is a solid side-by-side reference when you compare blends at the supplier.

Choosing the Wire

Most shops run ER70S-6 solid wire on carbon steel. The “70” is tensile strength in thousands of psi, so ER70S-6 is rated at 70,000 psi. The “S” means solid, and the final digit reflects silicon and manganese content, with the 6 being the higher, better-wetting grade most people buy. Common diameters run 0.75 mm to 2.25 mm depending on thickness and power source, as covered in the OpenLearn guide to gas-shielded arc welding.

When the steel is dirty, rusty, or the fit-up is unpredictable, E71T-1 flux-cored wire is the better tool. The “T” means tubular, and the flux core decomposes into shielding gas and slag, so it welds without a separate shielding cylinder. It is slower and spatterier, but it forgives scale, oil and out-of-position work in a way solid wire cannot.

The Four Transfer Modes

Transfer mode describes how the molten wire drops into the puddle. The machine switches modes automatically as amperage changes, and each has its own sound, thickness range and position limits.

• Short circuit. The wire touches the puddle, an electrical short forms, the tip melts and retracts, and the cycle repeats 90 to 200 times per second. That crackling “bacon frying” sound tells you wire feed speed and voltage are in harmony. Change one without the other and the sizzle becomes a putt-putt or a loud bang.
• Globular. Larger droplets fall one at a time with visible spatter. Limited to flat and horizontal fillet welds in material about 1/8 in. (3 mm) or thicker, and the mode that fills gaps and bridges joint variation.
• Spray. Small droplets transfer axially into the puddle and the arc sounds like a steady hum. The bead is smooth and wide with very little spatter, and on a hand-held gun it is limited to 1/8 in. (3 mm) and thicker material in flat and horizontal fillet positions. It is the fastest, cleanest mode in the process.
• Pulsed spray. A pulsing power source switches spray on and off thousands of times per second, controlling heat input tightly enough that one setting handles thin sheet without burnthrough and thick plate with deep penetration, while removing most of the spatter a conventional spray weld throws.

Aluminium: Where MIG and MAG Get Hard

Aluminium inverts the usual rules. It conducts heat far better than steel, so it burns through before it soaks in. Its weld metal is more susceptible to porosity, and gas porosity is what you meet first. Aluminium GMAW is also more than ten times more sensitive to changes in wire feed speed than steel, so a forgiving settings window on a mild steel trailer frame becomes razor thin.

Two habits fix most of it. Push the gun along the joint rather than pulling it, keeping the arc on the leading edge of the puddle for better penetration and bead shape. And get the wire off the direct spool with a spool gun or remote feeder, because a push-pull gun or a short liner is not accurate enough for aluminium. Prep matters too: a dedicated aluminium cleaner and a separate stainless brush, since contamination on the joint comes back as porosity. Our aluminium cleaner prep guide covers the cleaning procedure, the complete aluminium MIG guide walks through settings and feeder options, and aluminium flux-cored wire has its own rules in our guide to aluminium flux welding.

TIG Deep Dive: Tungsten, Polarity, AC Balance, and Filler Rod

TIG is the process people romanticize and get wrong most often. It asks you to control four independent variables at once with two hands, one foot, and a helmet that never shows you the whole picture. Where MIG hands you a trigger that does most of the thinking, TIG hands you a torch and says: your call.

The tungsten electrode is a tool, not a filler

In TIG the tungsten electrode is never consumed. It does not melt into the weld. It carries the arc, and filler metal arrives separately, fed by hand from a rod. That single design choice explains almost everything TIG is good and bad at: extraordinary control and cleanliness on one side, slow deposition and unforgiving technique on the other.

Electrode selection is a short list. Traditional electrodes are tungsten with roughly 1% thoria added, per OpenLearn’s breakdown of gas-shielded arc welding processes, though thoriated tungsten has largely given way to safer alternatives:

• Pure (green) — classic for DC work on aluminum and magnesium, though modern inverter machines made it less necessary.
• Ceriated (grey/orange) — works on DC and AC, ignites at lower voltage, holds a balled tip well.
• Lanthanated (gold/blue) — the modern replacement for 1% thoriated. No radioactive dust concerns and a sharper point on AC.
• Thoriated (red) — still respected for DC steel work, but the grinding dust is a health concern most shops now avoid.

Polarity: the setting that decides everything

Polarity is where TIG separates itself from MIG and MAG. In MIG the electrode is positive almost always. In TIG the direction of current flow changes what the arc does, and the material picks your setting for you.

Polarity	What it does	Best for
DCEN (electrode negative)	Most heat goes into the work; the tungsten stays cool and keeps a sharp point	Carbon steel, stainless, copper and its alloys, nickel alloys, titanium, zirconium
DCEP (electrode positive)	Heat concentrates in the tungsten; the arc blasts surface oxide off the work	Used only briefly for cleaning aluminum oxide, never as a main welding setting
AC (alternating)	Half-cycles share cleaning and penetration duties	Aluminum, magnesium, aluminum bronze

DCEN is the workhorse. On steel, stainless, copper, nickel, titanium and zirconium it delivers deep penetration and lets you keep a needle-sharp tip, which is where TIG’s famous precision comes from. Flip to DCEP and you get an aggressive, shallow-cleaning arc that turns a pointed tungsten into a mushroom in seconds. That’s why nobody welds aluminum on DCEP.

AC and the balance control nobody explains

Aluminum oxidizes instantly, and that oxide melts at a temperature far above the base metal. TIG solves it with alternating current: the positive half-cycle breaks the oxide apart, the negative half-cycle dives in and penetrates. Cleaning and fusion from a single arc.

A conventional sine-wave machine alternates by nature and is roughly balanced. A modern square-wave machine lets you dial it, and that control quietly transforms results:

• About 70% electrode negative — deeper penetration, less heat into the tungsten.
• About 45% electrode negative — more oxide breakdown, useful on heavily oxidized or cast aluminum.

Square-wave AC isn’t only about balance. Compared with a conventional sinusoidal waveform, it can increase TIG welding speed by roughly 50–75%, because the current crosses zero faster and the arc spends more time working instead of flickering through the transition.

Filler rod: picking the metal that goes in the joint

Because TIG filler arrives by hand, matching rod to base metal is a decision you make before you ever strike an arc. Get it wrong and a beautiful weld can fail metallurgically.

Base material	Common filler	Notes
Carbon steel	ER70S-6, ER70S-2	ER70S-2 gives better deoxidation on dirty or rusty steel
Stainless steel	ER308L	Match grade to parent; L = low carbon for corrosion resistance
Aluminum (3000/6000 series)	ER4043	The default aluminum TIG filler; easier to run, slightly less strength
Aluminum (5000/7000 series)	ER5356	Stronger, better for anodized work; less forgiving on thin material

Rod diameter should roughly match your joint size and amperage: thin sheet takes 1/16 in. (1.6 mm) rod, plate work moves up from there. Technique matters as much as alloy. Feed the rod into the leading edge of the puddle, angling the arc toward the puddle rather than the rod, so the filler melts cleanly instead of bridging the arc and splattering. A good TIG welder watches the puddle, not the arc, and the rod appears where the puddle is about to move.

For aluminum, prep is non-negotiable. Surface contamination is the enemy, and a dedicated aluminum cleaner for welding removes the oils and oxides that cause porosity before they ever reach the arc.

Where TIG stops making sense

TIG costs you time in two places: deposition and preparation. Because you add filler by hand and the electrode never melts, your deposition rate sits well below MIG/MAG. And because quality seams demand joint edges free of rust, oil, grease and impurity before the arc is struck, prep time balloons.

Fronius puts a hard number on the economic ceiling: TIG becomes uneconomical for material thicker than about 4 mm, while MIG/MAG covers everything from ultra-light sheet to solid plate. That is a throughput statement, not a knock on quality.

Shielding gas is almost always argon, the default for TIG. Two mixtures are worth knowing: argon/hydrogen for austenitic stainless steel, where added hydrogen boosts heat and fluidity, and argon/helium for aluminum, copper and nickel, where helium’s higher energy raises heat input on thick sections.

If your aluminum work leans toward thicker sections or you are chasing production speed, read up on aluminum MIG welding. A spool gun will outrun a TIG torch on every thick aluminum job in the shop. TIG’s domain is precision, not pace.

Head-to-Head: Which Process Wins for Which Job?

Now put them side by side. The table below compares TIG (GTAW), MIG (GMAW with an inert gas blend), MAG (GMAW with an active gas blend) and, for context, stick (SMAW) across the factors that actually decide which process you should be holding at the end of the day.

Factor	TIG (GTAW)	MIG (GMAW, inert gas)	MAG (GMAW, active gas)	Stick (SMAW)
What it melts	Base metal, hand-added filler rod	Base metal, continuous consumable wire	Base metal, continuous consumable wire	Base metal, consumable stick electrode
What protects the weld	Inert gas from the torch cup (argon or helium)	Inert gas blend (90/10, 100% argon)	Active gas blend (75/25, pure CO2)	Flux slag from the electrode coating
Typical materials	Stainless, aluminum, magnesium, copper, titanium	Carbon steel, stainless, aluminum	Carbon steel, structural and heavy plate	Carbon steel, stainless, field repairs
Thickness range	Sheet to roughly 4 mm	Ultra-light gauge to thick plate	Ultra-light gauge to thick structural plate	Roughly 3 mm and up
Deposition rate	Low	High	Highest of the three	Low to moderate
Spatter	Very little	Little with 90/10, more with 75/25	Moderate to heavy	Moderate, plus slag to chip
Learning curve	Steepest; puddle held by hand	Moderate	Most forgiving of the gas processes	Moderate and forgiving
Joint cleanliness	Demanding; oxide-free metal	Moderate	Lower; tolerates light rust	Least demanding
Typical use	Thin, cosmetic, high-purity seams	Sheet work, stainless, general fabrication	Structural steel, production throughput	Site work, repair, no gas required

Both MIG and MAG fall under GMAW, which is why the two columns look so similar. The difference is entirely in the gas.

Speed and productivity

MIG and MAG win this one, and not narrowly. The wire feeds continuously while the arc stays lit, so nothing waits on a consumable to melt down. Because MIG/MAG supports both semi-automatic and fully automatic operation, it dominates production throughput, and the wire and equipment handling that make it fast is well documented in manufacturer guidance such as Miller’s GMAW guidelines. TIG is the slowest of the three by design, because torch angle, filler placement and puddle size are all under manual control.

Cosmetic and metallurgical quality

TIG generally produces the highest-quality seam: narrow, even beads, controlled penetration and a surface that usually needs little finishing. MIG and MAG can also achieve very high quality, but TIG gets there with less cleanup. Worth noting: unlike stick, MIG/MAG and TIG deposit no flux slag, so there is no slag to chip, grind or clean off the finished joint.

Cost per inch of weld

TIG is the most expensive way to fill a joint. The arc is short, you spend more time per inch, you burn more shielding gas, and you add filler metal by hand. On a structural contract that labour gap can dwarf the cost of the consumables. MIG/MAG pays for itself in cycle time.

Position of the workpiece

Flip the job vertical or overhead and the ranking shifts. TIG is far more forgiving there because the puddle is controlled by hand and filler is fed precisely into the pool. MIG/MAG runs out of position perfectly well, but spray-transfer MIG on a vertical stainless seam takes real skill, which is why flux-cored wire is the usual out-of-position answer. Stick still has a strong claim, as the case for why SMAW still wins makes clear.

Material range

TIG reaches the metals that fight back: aluminum, magnesium, copper, titanium, thin stainless and dissimilar combinations. MIG/MAG is the workhorse for carbon steel production work, and with a spool gun it handles aluminum well too, as our complete guide to aluminum MIG welding shows. Simply put, MIG/MAG covers everything from ultra-light gauge sheet to thick structural plate, while TIG is the specialist choice for thin, delicate or high-purity work.

Safety and fume

The fume numbers favor TIG, and the gap is wide. An EPRI study cited by NIOSH reported full-shift geometric mean hexavalent chromium exposures of 1.4 µg/m³ for SMAW, 1.3 µg/m³ for GMAW and just 0.14 µg/m³ for GTAW. TIG generates roughly a tenth of the Cr(VI) of the other two. That gap matters, because NIOSH recommends an 8-hour TWA limit of 0.2 µg/m³ for all Cr(VI) compounds, far below the OSHA permissible exposure limit of 5 µg/m³ set in 29 CFR 1910.1026. On stainless work, TIG is the lower-fume choice by measurement.

Choosing and Setting Up Your Machine: Parameters That Actually Matter

You have picked the process. The machine matters, but the setup matters more. Most bad MIG/MAG and TIG welds were decided before the arc ever started, by a wire feed speed, a voltage, or a stickout that was wrong from the first inch.

Constant Voltage vs. Constant Current (and Why a Combo Machine Wins)

The two processes need fundamentally different power supplies, which is why a straight MIG box cannot run a decent TIG arc.

• MIG/MAG needs constant voltage (CV). The machine holds voltage steady while current floats with wire feed speed. That self-regulation lets you change current mid-bead by moving the gun closer to or farther from the work.
• TIG needs constant current (CC). Arc length changes constantly by hand, so the power source must hold amperage steady as resistance shifts. A CV machine running TIG would wander badly.
• A combined CC/CV inverter does both. Modern multi-process inverters switch modes digitally, which is why they are the default for anyone who wants more than one process off a single box.

Specs from this class of machine: MIG output runs from about 8 A / 8.0 V up to 500 A / 44 V, and TIG from roughly 4 A / 10.2 V to 500 A / 30 V. The duty cycle is often the number that actually limits you: this class of equipment is typically rated 500 A at 60% duty cycle and 400 A at 100%, so at full 500 A you weld six minutes out of every ten before thermal protection trips. Running hot all day? Buy headroom you never plan to use.

Set It in This Order: Amp, Wire, Feed, Voltage

Beginners adjust voltage first because it is the dial that changes the sound. That is backwards.

1. Material thickness to amperage. Thickness sets how much heat you need, and therefore your baseline current.
2. Wire diameter to current range. Pick a diameter whose published range covers that current, then set feed speed inside it.
3. Wire feed speed to penetration. Feed speed controls how much metal and current you push into the joint.
4. Voltage to bead width and height. Voltage trims arc length and therefore bead shape, not weld depth.

Miller publishes a wire feed speed reference that makes step three concrete. At 0.023 in. wire, the practical range is 30–90 A at about 3.5 in. of wire feed per amp. At 0.030 in., it is 40–145 A at 2 in. per amp. At 0.035 in., it is 50–180 A at roughly 1.6 in. per amp. Worked example: 1/16 in. (1.6 mm) material calls for about 62.5 A, which on 0.035 in. wire works out to roughly 100 ipm, a starting point rather than a final answer.

Voltage is where most people overshoot. Too low and the wire stubs into the work, pushing the gun back at you. Too high and the arc destabilizes, spattering and widening without going deeper. Aim for the midpoint between those two failures. The full Miller guidance on GMAW setup lays out the theory.

Stickout, Standoff, and Gun Angle

Three physical numbers decide whether a well-tuned machine deposits a good weld.

• Electrode extension (stickout): 10–15 times the wire diameter. Too short risks burn-back, where the wire fuses to the contact tip. Too long causes stubbing, especially at weld start.
• Nozzle standoff: 6–13 mm (1/4 to 1/2 in.) from the work for adequate gas coverage. Push closer and spatter plugs the nozzle; pull back and shielding gas scatters before it reaches the puddle.
• Gun angle: 0–15 degrees from perpendicular for best penetration. Dragging steeply drops penetration and lays a cold, tall bead.

Aluminum tightens these tolerances. It is far more sensitive to wire feed rate changes than steel, which is why a spool gun and a push technique setup matter so much on thin sheet.

Gas Cylinders, Regulators, Flowmeters, and Flow Rates

Shielding gas is only as good as the delivery system feeding it.

• Cylinder selection. Match cylinder and regulator to the gas family, and never trust a color-coded cap alone. Read the label and the CGA fitting.
• Regulator and flowmeter. A two-gauge regulator shows cylinder and delivery pressure; a flowmeter reads flow in CFH or L/min. Set gas with the flowmeter, because that is what you control at the arc. A wandering needle usually means a leak, a loose fitting, or a regulator in the sun.
• Practical argon flow rates. For TIG, roughly 10–20 CFH is the usual band, adjusted for cup size and draft. More gas is not better; excessive flow creates turbulence that pulls air into the shield.

If you are comparing cylinders, regulators, and gas suppliers for the first time, our gas buying and safety guide covers the cylinder and delivery decisions in detail. Fix delivery problems before chasing porosity at the puddle.

Common Mistakes and How to Fix Them

Welding defects are diagnostic. The bead shows what the arc did, and once you can read it, most faults are corrected in under a minute. Beginners respond to a bad bead by randomly turning knobs instead. The logic below follows published cause-and-corrective-action tables in the Lincoln Electric MIG problems and remedies guide and Hobart’s MIG troubleshooting reference.

MIG and MAG: Spatter, Porosity and Bead Shape

Symptom	Likely cause	Corrective action
Excessive spatter	Feed speed too high for the voltage, high voltage, long stickout, low gas flow, dirty wire or work	Rebalance feed speed and voltage, shorten stickout, raise gas flow, clean wire and plate
Porosity	Poor shielding, spatter in nozzle, hose leaks, drafts, wrong gas, wire past nozzle	Fix leaks, clear nozzle, shield from wind, match gas to material, hold gun close at weld end
Undercut	Wrong gun angle, excessive voltage, fast travel, arc blow	Re-angle gun, lower voltage, slow travel, move work lead clamp
Lack of fusion / cold lap	Wrong gun angle, travel speed, insufficient heat	Aim arc at joint edge, slow down, add heat
Burn-through	Excessive heat input	Lower voltage range, reduce feed speed, steady travel
Waviness	Unsteady hand, no gun support	Brace gun on work or sled, hold travel speed steady
Distortion	Excessive heat, long welds, poor fit-up	Restraint, tack welds, lower heat, faster travel, cool small segments

Spatter is the first fight every new MIG/MAG welder has, and the fix is almost always the voltage-to-wire-feed-speed balance. Raise feed speed and voltage must rise with it to hold a stable arc length; if not, the wire touches the puddle, shorts out and throws molten droplets. Voltage that is too low relative to feed speed is the main culprit, and a long stickout sprays wider. Older constant-speed feeders need a constant-voltage source, while a voltage-sensing feeder runs on either a constant-voltage or constant-current machine.

Porosity looks like gas bubbles or open pits, and it is nearly always a shielding problem. Check the gas hose for leaks at the regulator, the flowmeter and the gun, and shield the area from wind: a cross-draught strips shielding gas off the puddle in seconds. Wire sticking too far past the nozzle exposes it to the air, and at the end of a joint the open pool oxidizes. Hold the gun close to the bead until the metal solidifies.

Undercut is a groove chewed along the toe of the bead. Arc blow is the other culprit, showing as erratic spatter in one area when the magnetic field around the work lead shoves the arc sideways. Move the work lead clamp, or change your travel direction relative to it.

Lack of fusion and cold lap mean the molten metal never melted into the base metal. Aim the arc at the leading edge of the joint, slow your travel, and make sure voltage is not so low that the arc is crawling. Burn-through is the opposite failure and arrives quickly on thin material: use a lower voltage range, reduce wire feed speed, and keep a steady travel speed so the puddle does not sit in one place. Distortion is a heat-management problem, not a machine-setting one. Restraint, tack welds, lower heat input, faster travel and small segments allowed to cool are the standard remedies, and back-stepping keeps long seams from cooking out of flat.

TIG: Tungsten and Puddle Problems

TIG fails differently because the operator, not the machine, controls the puddle. Most faults trace to four things.

• Tungsten contamination and inclusions. Touching filler rod to the tungsten, dipping the electrode into the puddle or overheating it puts tungsten into the weld, which can show as a dark spot, pit or crack. Keep the hot end deep in the shielding gas and never touch filler metal.
• Electrode overheating on AC. A balance set too far toward electrode positive overheats the tungsten and balls it up. Drop the amperage or move toward more electrode-negative balance. Lanthanated and ceriated electrodes tolerate this far better than plain tungsten.
• The wrong grind for the current type. DC work wants a flat or bevel ground tungsten; AC needs a pointed or combination grind that splits the arc. The wrong preparation causes wandering arcs and erratic penetration, so follow the published electrode preparation guidelines for your machine.
• Porosity. Low gas flow, a cracked or loose cup, or a torch pointed into the wind starve the puddle of shielding. Fix the flow and the cup before blaming the filler metal.

Aluminum adds its own porosity problem, because the oxide layer reforms in seconds. Oxide left on the edge or the filler rod turns into gas in the puddle. Use dedicated aluminum wire and clean the joint immediately before welding, as explained in our guide to aluminum cleaner for welding. See also the complete aluminum MIG welding guide and our all-position welding rod guide.

Then the classic beginner error: scratching the tungsten on the workpiece to strike an arc. It leaves inclusions in the joint, contaminates the work and wears the electrode. Use the machine’s high-frequency start or a lift-off start instead.

Seven Mistakes Beginners Make on Day One

1. Welding dirty metal. Mill scale, rust, oil and paint cause slag, spatter and porosity. Clean the joint before you light the torch.
2. Wrong shielding gas or flow rate. 75/25 suits carbon steel short-circuit work; 90/10 or pure argon suits spray and stainless.
3. Changing voltage when the fault is feed speed. Get feed speed right first, then trim voltage. Random knob turning burns hours.
4. Too much stickout or standoff. Wire at 10 to 15 times its diameter, nozzle roughly 6 to 13 mm from the work.
5. Setting amperage by habit. A 3 mm plate and a 12 mm plate cannot share the same settings.
6. Travelling too fast. It causes undercut, lack of fusion and burn-through in thin material. Slow down and let the puddle move.
7. Ignoring fume extraction and PPE. Welding fume can injure your lungs long before you notice anything. Keep the extractor near the plume and wear the right helmet lens shade.

Welding Safety: Fume, Hexavalent Chromium, Fire, and Cylinders

Most shop injuries are loud: a flash burn, a cylinder rolling off a truck, a sleeve catching fire. The injury that actually ends careers is the invisible one. Welding fume sits in the air you breathe, and according to OSHA’s welding fact sheet, the metal you are fuming can leave you with permanent lung damage.

What Welding Fume Does to You

Welding fume is a mix of metal oxide particles, gases and vapors, and a single weld can produce a plume dense enough to see across a garage. Short-term symptoms are familiar: eye, nose and throat irritation, coughing, dizziness, nausea. Some welders develop metal fume fever, a flu-like reaction that shows up hours after exposure with chills, fever, chest tightness and aches.

The long-term picture is worse. Prolonged exposure to welding fume can damage the lungs and raise the risk of cancers of the lung, larynx and urinary tract. Fume also carries manganese, and long-term manganese exposure is associated with Parkinson’s-like neurological symptoms. That is why “just weld in the garage with the door open” deserves a second look.

Hexavalent Chromium: The Hazard You Cannot See

Hexavalent chromium, or Cr(VI), is the contaminant OSHA regulates specifically for welding. It is a component of stainless steel, many nonferrous alloys and chromate-bearing coatings. During welding, intense heat oxidizes metallic chromium in the base metal and converts it to the far more toxic Cr(VI) form, so Cr(VI) can be generated even when the material contained only metallic chromium before the arc struck.

NIOSH reports that welders are the largest group of workers potentially exposed to Cr(VI) compounds. Under 29 CFR 1910.1026, OSHA sets a permissible exposure limit of 5 µg/m³ as an 8-hour time-weighted average, with an action level of 2.5 µg/m³ that triggers monitoring obligations. Critically, the standard requires engineering and work practice controls first, with respiratory protection used to supplement them when feasible controls cannot reach the limit. A respirator is the last layer, not the first.

Controls That Actually Work

• Clean the workpiece first. Strip paint, coatings, rust, mill scale, oils and any chromate-bearing finish before the arc strikes. Vaporized coating is fume you did not have to make. Our guide to prepping aluminum with a dedicated cleaner shows how demanding surface preparation really is.
• Position yourself upwind outdoors. OSHA is explicit that welding outdoors or in open work spaces does not guarantee adequate ventilation, because the breeze can carry the plume straight back at you.
• Use local exhaust ventilation. A fume extractor gun or hood positioned close to the plume beats a fan pointed at the door. See OSHA’s guidance on controlling Cr(VI) exposure.
• Consider a lower-fume process or consumable when the material is dirty, coated or heavy.

Asphyxiation: The Silent Danger in the Bottle

Shielding gases are the second hazard most hobbyists underestimate. Argon, helium and carbon dioxide all displace oxygen. In a poorly ventilated space, a leak or an open cylinder valve can drop oxygen levels until a person becomes confused and collapses without understanding why. Carbon monoxide can also form as an asphyxiation hazard during hot work in inadequate ventilation. This risk scales with room size, not weld size.

PPE: Shade Numbers, Gloves and Clothing

Eye protection comes first. Use ANSI Z87.1-rated eye and face protection, and pick the lens shade to match your amperage. The shade number system runs from lighter numbers for low-current work up to #13 and #14 for heavy arc work, and auto-darkening helmets let you start light and darken instantly. Wear flame-resistant clothing, leather gloves and sleeves, and hearing protection. Synthetics melt, and a melted shirt is a burn.

Fire: Hot Work Without the Burndown

Hot work practice is codified in NFPA 51B: move flammables at least 35 feet from the work, shield or cover anything you cannot move, and keep a fire watch in attendance for the duration plus a period afterward. Have a suitable extinguisher within reach, and treat a hot work permit as a real document in a shop with a contract. Sparks travel further than people expect, landing in floor voids, ductwork and adjacent shops.

Cylinders: Treat Argon Like a Propane Tank

Store cylinders secured upright with protective caps in place, in a cool, ventilated location, and never in a vehicle or enclosed space that is not ventilated. Full cylinders get the same respect as a propane tank. A regulator, hoses and cylinders are covered in more depth in our welding gas supply and cylinder safety guide, and supplier-side basics in this overview of welding gas services and safety.

Real-World Scenarios: Garage Project, Farm Repair, Stainless Tank, and Aluminum Trailer

Theory only gets you so far. The right process depends on the metal, its thickness, what the joint must survive, and who inspects it. Here are five jobs and the process that holds up on each.

Scenario One: The Weekend Trailer Frame

A mild steel trailer frame in a home garage is the classic MIG/MAG case: thick enough to absorb heat, mostly flat-position fillets and butt welds, no microscope inspections. Dozens of cuts and a hundred welds make speed the priority.

Run 0.035 in. ER70S-6 solid wire on 75/25 shielding gas for a forgiving arc with good penetration on 3/16 in. and 1/4 in. material. On 14 and 16 gauge wall tube, switch to 90/10 for a cleaner bead, less spatter, and faster travel without burn-through.

Trouble here is fit-up, not gas. Gap the plates more than the wire diameter and you burn through before the puddle fills the joint. Clamp, tack, check the gap, weld continuously.

Scenario Two: The Farm Repair Shop

Rusted loader buckets, mower decks, implements still wearing paint and grease, fit-up that is whatever it happens to be. Flux-cored wire earns its keep: no shielding gas, so wind, drafts and long hose runs stop being problems, and it handles out-of-position work better than solid wire, which suits a bucket welded on its side.

Surface condition still matters, differently. MIG/MAG tolerates some contamination, particularly with metal-cored wire, but rust and mill scale raise spatter and porosity risk because they absorb moisture and gas. Mill scale is the harder one: dense, floating on the puddle, resistant to wetting, it acts like a mini shield over the molten metal. Grind it back to bright metal wherever you can.

Scenario Three: The Stainless Food or Chemical Tank

A stainless tank seam is judged by more than strength. The interior has to be cleanable and corrosion resistant, so a MIG bead with overlap, spatter or a crevice is a sanitation problem before it is a metallurgy one.

TIG gives a single, narrow, fully fused seam with no spatter and no bead profile to trap product, which is why stainless tank and pipe work is overwhelmingly TIG. For 304 and 316 stainless, ER308L filler is standard, its low carbon reducing sensitisation risk in the heat-affected zone.

• Purge gas. Argon behind the joint; without it the root oxidises and the underside goes brown or black and corrodes.
• Filler selection. Match the filler to the parent metal, not just the grade name.
• Heat tint. Stainless TIG welds tint by nature. The band is not a defect but a record of thermal history, and inspectors read the colour gradient to judge whether heat input stayed in range.

Keep heat input low, gas flowing, and the joint clean before you light the torch.

Scenario Four: The Aluminum Trailer or Boat

Aluminum changes the answer entirely. It conducts heat far better than steel, carries a tenacious oxide layer, and melts close to the filler’s melting point, so everything is about control.

For thin panels TIG is standard. For thicker sections and production work, MIG with a spool gun or push-pull feeder controls the softer, more conductive aluminium wire, which buckles and kinks if pushed through a standard gun cable. Push technique, wire angled into the joint, oxide cleaned beforehand. Our aluminum cleaner for welding guide covers prep in detail.

For the repairs searched for most: the aluminum boat welding guide for hull joint technique, the complete aluminum MIG welding guide for wire and gas selection, and the alloy wheel welding guide for cast wheel repair.

Scenario Five: The Coded Production Contract

On coded work the process is not a matter of taste. AWS D1.1 requires qualified welding procedures and welder qualification for structural work, so parameters come from the specification, not operator preference. A welder who can hit a good bead all afternoon still cannot deviate from the WPS: if it specifies flux-cored wire at a set feed speed and voltage window, that is the process.

MIG/MAG dominates on throughput. Deposition rates of 1.25 to 7.5 kg/h are far higher than anything TIG can match on the same joint, and in a production shop cycle time is money.

Illustrative Cost and Time Comparison

A clearly labelled illustration of a 3 m fillet weld on 6 mm mild steel: why TIG costs more per metre even when both welds are code compliant. Typical shop figures, not quoted rates.

Factor	MAG (flux-cored, 1.2 mm)	TIG (ER70S-6, 2.4 mm)
Arc-on time, 3 m	About 6 minutes	About 14 minutes
Consumables per metre	Lower	Higher (more filler used)
Shielding gas	None	Argon, higher flow
Cost per metre	Lower	Roughly 2 to 3 times higher

The TIG weld is not better, just slower and pricier per metre. On a code-compliant frame the fast process wins; reserve TIG for where surface finish, the metal, or heat control demands it.

Conclusion: Pick the Process, Then Master It

Choosing a process is not a personality test. It is four questions asked in order: what are you welding, how thick is it, what position is the joint in, and what quality standard must the finished seam meet? Answer those and the process picks itself.

Here is the rule set in the shortest form it survives.

The job in front of you	Reach for	Because
Thick carbon steel, production volume, imperfect fit-up	MIG/MAG	Fastest cycle time, forgiving of grime, widest range of positions
Thin material, stainless, aluminum, copper, cosmetic seams	TIG	Heat control is all in your hands and the puddle stays where you put it
Heavy steel on a budget, or a shop already stocked with CO2	MAG	Same machine as MIG, cheaper gas, handles thick material well
Field repairs where no cylinder travels	Stick	No gas, little cleanup, and the machine goes where you go

That last row deserves a fair hearing, because stick remains the most portable option available. Our guide to why SMAW still wins in the field makes the case well.

One wrinkle beginners miss: MIG/MAG covers solid wire and flux-cored wire alike. On carbon steel, flux-cored deposition beats stick for speed, and self-shielded flux-cored wire runs with no gas bottle, which blurs the field-repair line in the table above.

Start with MIG/MAG on Mild Steel, Add TIG Second

Learn MIG/MAG first, on mild steel, for one reason: feedback. The machine manages arc length, so what you really control is travel speed and gun position. Both show up within seconds, and a bead goes from ugly to decent in an afternoon. TIG is the opposite trade. Nothing is automatic; arc length, puddle size, filler placement and balance control are separate skills that take weeks to feel natural. It is worth earning, because TIG unlocks aluminum and thin-gauge work, but it comes second, not first.

When you do get there, remember that chemistry beats technique on aluminum. Prepping aluminum properly before you strike an arc does more for the finished bead than any tip in this article.

The Quiet Argument for Keeping TIG in Your Toolkit

Welding fume is the hazard that quietly follows a hobbyist home. The EPRI exposure study cited by NIOSH measured geometric mean hexavalent chromium exposures of 1.4 µg/m³ for SMAW, 1.3 µg/m³ for GMAW and 0.14 µg/m³ for GTAW. Of the three, TIG generates the least.

One thing does not change: both MIG/MAG and TIG are gas-shielded, so both need a cylinder, a regulator and a flow rate you actually set. Stick needs neither. If you are outfitting a shop, choosing shielding gas and cylinders is a decision you will live with for years.

Four Habits That Separate Consistent Welders from Frustrated Ones

1. Clean the metal. Grind or wire-brush back to bright material. Paint, rust, oil and mill scale are the cheapest defects to prevent and the most expensive to fix later.
2. Match the gas to the material. 75/25 for carbon steel, 90/10 for stainless and spray transfer, pure argon for aluminum. Wrong gas shows up as spatter or porosity, and it is never a machine fault.
3. Set wire feed speed before voltage. Voltage too low for the wire feed speed is the top cause of spatter, and raising voltage to compensate only makes it worse.
4. Keep a steady travel speed. Waviness, undercut and inconsistent bead height trace back to a hand that speeds up and slows down. Brace the gun and let it move at one speed.

Those four are the controllable variables behind most weld defects. Everything else is a symptom.

Now pick a joint on your own bench and choose for that job, then spend a month getting the gas, wire and machine settings right, because that is where the skill lives. Continue with our all-position rod guide for filler selection and our aluminum flux-core breakdown when you want the flux route on non-ferrous work.

Frequently Asked Questions

Is MIG and MAG actually the same welding process?

Yes. MIG (metal inert gas) and MAG (metal active gas) are both gas metal arc welding, AWS process 13. The only technical difference is the shielding gas: an inert gas such as argon for MIG, and an active gas such as CO2 or an argon/CO2 blend for MAG. Americans say MIG, while European and Australian standards use MAG as the generic term.

Which is better for a beginner: MIG, MAG, or TIG?

Start with MIG/MAG on mild steel. It has the fastest feedback loop, the widest range of consumables and accessories, and a forgiving learning curve. TIG rewards the same hand-eye coordination and cleanliness discipline, but it adds a separate skill set — puddle control and filler timing — that pays off later on thin, stainless and aluminum work.

Is a TIG weld stronger than a MIG weld?

Not inherently. Weld strength is governed by the filler metal, joint design, heat input and fit-up, not the process name. TIG generally produces a narrower, more controlled heat-affected zone and a cleaner deposit, while MIG/MAG can achieve very high quality with the right procedure. In a coded structural application, follow the qualified procedure rather than the process label.

What shielding gas should I use for MIG welding mild steel?

A 75% argon / 25% CO2 blend is the most common all-around choice for short-circuit transfer on carbon steel, and it works in all positions. A 90% argon / 10% CO2 blend gives cleaner, more consistent transfer with less spatter and is preferred for thinner material and stainless. Pure CO2 is cheaper and works everywhere but produces more spatter and requires more voltage.

Can TIG weld aluminum, and what does it take?

Yes, and TIG is the traditional process for aluminum because the oxide layer needs AC current to break down cleanly. Use AC with a balance setting around 45% electrode negative for cleaning, clean the oxide thoroughly with a stainless wire brush, use an argon/helium mix for thicker sections, and match the filler rod to the alloy — ER4043 for 3000 and 6000 series, ER5356 for 5000 and 7000 series.

Why is my MIG weld spattering so much?

The most common cause is a voltage that is too low for the wire feed speed you are running, which makes the wire stub into the puddle and explode. Other causes include excessive wire feed speed, too high a voltage, an electrode extension that is too long, dirty or oily wire, a dirty workpiece, and insufficient shielding gas. Fix the wire feed speed first, then trim the voltage.

Do I need a separate TIG machine if I already own a MIG welder?

Not necessarily. Many multi-process inverters run TIG on the same box by switching to constant-current mode and adding a TIG torch, though you need HF start or lift-arc capability for reliable ignition. A dedicated TIG machine is worth it only if TIG is a large share of your work and you want features like square-wave AC, pedal control or high-frequency pulse.

Which process produces the least welding fume and the lowest health risk?

Based on an EPRI exposure study cited by NIOSH, GTAW/TIG produced geometric mean hexavalent chromium exposures of 0.14 µg/m³, versus 1.3 µg/m³ for GMAW and 1.4 µg/m³ for stick welding. That makes TIG the lowest-exposure of the three for stainless work, but ventilation and fume extraction still matter regardless of process.

Is TIG worth the extra cost and time for a hobbyist?

For visible, decorative or thin-gauge work, yes. TIG gives finer control of a small pool, which is what thin stainless, aluminum and small tubing need, and it produces a clean, corrosion-resistant bead with no spatter to grind off. For structural mild steel, MIG/MAG will get you to a good finished part far faster and for less money.

Can I weld stainless steel with MIG/MAG, or is it a TIG-only job?

You can, and in many production shops you should. Use a stainless wire such as ER308L with an argon blend —98% argon/2% oxygen or a tri-mix for stainless, or 90% argon/10% CO2 for carbon and stainless — and note that TIG generates far less hexavalent chromium fume. TIG is still the better choice for thin stainless, food-grade interiors and cosmetic seams.