What Metal Can You Weld? Mild Steel, Stainless, and Aluminum Basics

So, what metals can you weld? The short answer: most metals can be welded. However, the longer answer is that each metal has different requirements for process, filler, shielding gas, and technique. Using the wrong combination doesn’t just produce a bad weld — it can produce a weld that looks fine and fails under load.

In this guide, we cover the three metals you’re most likely to encounter as a home shop or farm welder — mild steel, stainless steel, and aluminum — plus a few others worth knowing about. Understanding what you’re working with before you strike an arc is one of the things that separates frustrating welding from productive welding.

Equally important, matching the metal to the correct process is a safety issue as much as a quality one. For instance, welding galvanized steel without ventilation releases toxic zinc fumes, while using the wrong filler on a load-bearing joint can create a weld that fails without warning. Therefore, the few minutes you spend identifying your material and confirming the right setup pay off in both weld quality and personal safety.

Mild Steel (Carbon Steel)

Generally, mild steel is the most weldable common metal. Moreover, it’s forgiving of imperfect settings, tolerates a range of processes, and doesn’t require exotic filler or shielding gas. Most farm equipment, structural steel, and home fabrication projects are mild steel.

Technically, mild steel is carbon steel with a carbon content below 0.30% — the low carbon content is what makes it ductile and weldable without preheat requirements on most thicknesses.

Processes: MIG, Stick, TIG, flux core — all work. MIG is the home shop standard.

Filler: ER70S-6 for MIG (0.035″ for most applications). E6011 or E6013 for Stick. ER70S-2 for TIG.

In practice, ER70S-6 is the workhorse wire for home shop MIG because it contains extra deoxidizers that help it tolerate the mill scale and minor surface rust you’ll encounter on real-world steel. Consequently, it produces a cleaner weld with less fuss than leaner wires. For Stick welding, E6011 digs through dirty or rusty material and runs on nearly any machine, whereas E6013 gives a smoother, better-looking bead on clean steel.

Shielding gas: 75/25 Ar/CO2 for MIG. 100% CO2 also works. 90/10 Ar/CO2 (C10) works well if you have a machine that will pulse MIG. No gas needed for flux core or Stick.

Preheat: Generally not required for mild steel under 1″ thickness at typical farm and home shop amperages. Heavier sections and high-carbon steels benefit from preheat — but standard A36 structural steel at normal thicknesses doesn’t need it.

Identifying Mild Steel

Most steel you encounter in farm and home shop work is mild steel. How to confirm:

• Sparks from a grinder: mild steel throws long, bright yellow-white sparks with bursts at the end
• Magnet test: mild steel is strongly magnetic (stainless can be magnetic or not depending on grade; aluminum is not)
• Color: raw mild steel is gray to blue-gray; hot-rolled has dark mill scale; cold-rolled is smoother and lighter
• If it came from a structural steel supplier or a farm equipment frame, it’s almost certainly mild steel

Stainless Steel

Stainless steel is an iron alloy with a minimum of 10.5% chromium content. The chromium forms a passive oxide layer that resists corrosion — that’s what makes it ‘stainless.’ In fact, welding stainless is manageable but requires more attention than mild steel.

The most common grades in home shop and farm work are 304 (general purpose, food-safe, most fabrication) and 316 (higher corrosion resistance, marine and chemical environments). For welding purposes, they’re handled similarly.

Processes: TIG preferred for appearance and precision. MIG with the right wire and gas works well for production and heavier work. Stick with 309 or 308 rod is viable for repairs.

Filler: ER308L for MIG/TIG on 304 stainless. ER316L for 316 stainless. Don’t use mild steel filler on stainless — you’ll compromise corrosion resistance.

Shielding gas: 98% Argon / 2% CO2 (also called 98/2) is the standard for stainless MIG. Tri-mix (Ar/He/CO2) is used in production. 100% Argon for TIG.

Heat management: Stainless conducts heat poorly, so heat builds up fast. This causes warping on thinner material and can reduce corrosion resistance in the heat-affected zone (called sensitization). Short passes, let it cool between passes, use heat sinks on thin material. Most common heat sinks are blocks of thick copper or aluminum.

Aluminum

Aluminum is light, corrosion resistant, and common in trailers, grain equipment, boat hulls, and automotive applications. However, it’s also the most challenging of the three to weld, for reasons that have nothing to do with skill level and everything to do with the metal’s properties.

Why aluminum is different: Aluminum has an oxide layer (aluminum oxide) that melts at roughly 3,700°F, while the aluminum beneath melts at 1,200°F. If you don’t remove or break through the oxide layer, you can’t get a proper weld. TIG welding uses AC current specifically to clean the oxide layer. MIG requires the gun to aggressively pierce it.

Thermal conductivity: Aluminum conducts heat roughly five times better than steel. Heat dissipates fast, which means you need higher amperage than the material thickness suggests, and you need to move quickly before the weld area becomes a heat sink.

Processes: TIG (AC) is the preferred method for aluminum — clean welds, precise heat control, handles thin material well. MIG with a spool gun works on heavier aluminum (3/16″ and up) and is faster. Standard MIG push guns can’t reliably feed soft aluminum wire without bird-nesting.

Filler: ER4043 for most general aluminum welding — flows well, good crack resistance. ER5356 for higher strength applications and 5xxx series base metals. Match the filler to the base metal when possible.

Shielding gas: 100% Argon. Always. No CO2 on aluminum — it causes porosity and a rough, contaminated bead.

Prep: Clean aluminum with a dedicated stainless wire brush immediately before welding to break up the oxide layer. Wipe with acetone first to remove oil and surface contamination. The same cleaning should be done with your filler metal as well. Aluminum picks up contamination fast — prep and weld quickly.

Realistically, many beginners find aluminum frustrating at first, and that’s normal. Because the metal conducts heat so aggressively and shows every flaw, it rewards practice more than any other common material. Consequently, if aluminum is your main goal, budget time for practice coupons before you commit to a real project.

Other Metals You’ll Encounter

Cast iron: Brittle, high carbon, very crack-prone when welded. Requires preheat (400–500°F minimum for most grades), slow cooling, nickel rod (ENi-CI) for Stick welding, and benefits from peening the weld. Cast iron repair is a specialty skill worth learning but not the starting point.

Galvanized steel: Zinc-coated mild steel. Welds like mild steel once the coating is removed from the weld zone. Never weld over the zinc coating without removing it and ensuring adequate ventilation — zinc oxide fumes cause metal fume fever. See our galvanized steel guide for the full breakdown.

High-strength and tool steels: Higher carbon and alloy content makes these crack-sensitive during welding. Generally require preheat and post-heat treatment. If you’re welding a component where failure would be dangerous (springs, load-bearing pins, cutting blades), know what you’re working with before you weld it.

Copper and brass: Can be welded with TIG or specialized processes, but require different filler, different gas, and technique adjustments. Not a common home shop task, but worth knowing they’re not just ‘metal you can’t weld.’

Quick Reference: Process and Material

What Metals Can You Weld With Your Machine?

Most beginner MIG machines — the Hobart Handler 140, Lincoln 140 HD, and similar — are designed for mild steel and can weld stainless with the right wire and gas. Aluminum requires either a spool gun attachment (available for most machines) or a TIG welder with AC capability.

Ultimately, what metals you can weld comes down to your machine as much as your skill. If you bought a basic 110V or 220V MIG machine, then your primary material is mild steel. Generally, that covers the vast majority of farm and home shop work. Moreover, stainless and aluminum are expandable capabilities that come with practice and the right consumables.