Welding Thin Materials: Best Practices for Steel, Stainless, Aluminium and Galvanised
March 16, 2022
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Welding Thin Materials: Best Practices for Steel, Stainless, Aluminium and Galvanised

Welding thin materials presents a specific set of challenges that do not apply to heavier section work. The goal on thin material is always the same: minimise distortion and spatter, prevent burn-through, and produce a sound weld with adequate fusion. Getting there requires the right process, the right consumable, the right gas, and the right technique — and the correct combination varies significantly depending on the base material.

This guide covers best practices for welding thin materials in carbon steel, stainless steel, aluminium, and galvanised steel — typically in the range of 0.5 mm (24 gauge) to approximately 5 mm (3/16 inch). Before starting any thin material welding job, establish the answers to these questions: What is the base material type and alloy? What is the material thickness? What is the surface condition — clean, scaled, galvanised, or coated? What welding position is required? What equipment is available? What is the operator's skill level?

Welding Thin Carbon Steel and Mild Steel

MIG/GMAW — short circuit transfer

For the thinnest carbon steel sheet — up to approximately 14 gauge (approximately 2 mm) — MIG welding in short circuit transfer (SCT) mode is the standard approach. Short circuit transfer produces low heat input, making it the most burn-through-resistant MIG transfer mode for thin material.

  • Wire diameter — use 0.6 mm (0.023 inch) diameter wire for the thinnest material; 0.8 mm (0.030 inch) for 14 gauge to 5 mm
  • Filler wire — ER70S-3 or ER70S-6 classification. For clean base materials, OK AristoRod 12.50 (ER70S-3 equivalent) is a clean-depositing option; for surfaces with light mill scale or contamination, OK AristoRod 12.63 (ER70S-6 equivalent) provides better tolerance
  • Shielding gas — 75% Ar / 25% CO₂ (M21) is the standard for short circuit on carbon steel; it gives good arc stability and a low spatter level
  • Torch angle — use a slight drag angle or neutral angle relative to the direction of travel; this produces the lowest spatter level in SCT mode

MIG/GMAW — pulse transfer

For applications where appearance, spatter level, or heat input control are priorities, pulsed MIG with a high-argon shielding gas (95% Ar / 5% CO₂, or Ar/O₂) gives significantly better results than short circuit on thin material. Pulse transfer provides excellent arc control, a wide operating range, and very low spatter — and is all-positional.

When welding in pulse mode, experiment with pushing or dragging the weld pool to determine which gives the best bead appearance for the joint configuration. Do not step back into the pool — this negates the pulse feature and produces an irregular bead. For the best pulse MIG results on thin material, use a machine with synergic pulse programmes — such as the Warrior Edge 500 DX with its THIN WeldMode, specifically designed to reduce spatter and distortion on thin plate.

FCAW — flux-cored wire

Flux-cored arc welding on thin carbon steel is possible but not ideal as a first choice. It produces a slag layer requiring removal, has lower deposition efficiency than MIG, and generates more smoke and spatter. Its main advantage is portability — self-shielded flux-cored wires require no external gas and run on DCEN (direct current electrode negative), which generates more heat in the wire than the base material, reducing burn-through risk. This makes self-shielded FCAW the best option for site welding of thin sections where gas shielding is impractical. See our flux-cored wire guide for more detail.

TIG/GTAW

TIG welding is the best process for low-volume or high-quality thin material applications. It produces no spatter, the best possible fusion, and the highest weld quality. It also allows autogenous welding (without filler) on very thin sections where the joint fit-up is tight and accurate. The trade-off is operator skill requirement and lower speed.

  • Tungsten — use a small diameter (2.4 mm / 3/32 inch) tungsten electrode ground to a fine point, ground parallel to the length of the tungsten. This produces a stable, concentrated arc on thin material
  • Shielding gas — 100% argon
  • Position — flat and horizontal are preferred. If vertical welding is unavoidable, vertical-down progression can produce a good result on thin material but requires practice; vertical-up is generally not recommended for thin section TIG

Welding Thin Stainless Steel

Thin stainless steel follows the same broad approach as carbon steel, with the critical addition of correct filler metal matching and appropriate shielding gas selection.

  • Preferred process — pulsed MIG gives the best combination of productivity and heat input control on thin stainless. If only short circuit is available, increase power source inductance (where adjustable) to improve weld pool control and reduce spatter
  • Filler metal matching:
    • Grade 304 base material → 308L filler
    • Grade 316 base material → 316L filler
    • Stainless to carbon steel dissimilar joint → 309L filler
    The 'L' (low carbon) designation is important — it reduces carbide precipitation in the HAZ and maintains corrosion resistance
  • Shielding gas — 98% Ar / 2% O₂ or 98% Ar / 2% CO₂ for MIG on stainless. Do not use the M21 (75/25 Ar/CO₂) gas used for carbon steel — the higher CO₂ content oxidises the weld surface and impairs corrosion resistance. For FCAW on stainless steel, 100% CO₂ or 75% Ar / 25% CO₂ is appropriate
  • Cleanliness — use dedicated stainless steel wire brushes and grinding discs. Carbon steel contamination on a stainless weld introduces corrosion sites that defeat the purpose of using stainless steel
  • Distortion control — stainless steel has lower thermal conductivity than carbon steel, meaning heat builds up more quickly and distortion is a greater risk on thin sections. Use tacking sequences, back-stepping, and intermittent welding to manage heat input

Welding Thin Aluminium

Thin aluminium is the most demanding of the common thin material applications, combining a low melting point, high thermal conductivity, and a refractory oxide surface layer that melts at approximately 2,050°C — far above aluminium's melting point of 660°C.

Pre-weld preparation is non-negotiable

Remove the oxide layer immediately before welding using a dedicated stainless steel wire brush (never use one that has been used on steel) or by chemical cleaning with acetone. The oxide layer will reform within minutes in ambient air, so weld promptly after cleaning.

Process and consumable selection

  • Filler wire — OK Autrod 4043 or OK Autrod 4047 for most 6xxx series base alloys and thin section work; OK Autrod 5356 where higher strength or anodising is required. Always match filler to base alloy. See our aluminium filler alloy selection guide
  • Shielding gas — 100% argon is standard for aluminium MIG and TIG. For thicker sections, Ar/He mixtures increase heat input and penetration, but for thin material 100% argon provides adequate results without the extra heat. See our article on argon vs helium for aluminium welding
  • Transfer mode — spray transfer is standard for aluminium MIG; pulse MIG gives better control on thin sections and is recommended where burn-through is a risk
  • Wire feeding — aluminium wire is soft and prone to birdnesting. A push-pull torch is strongly recommended for reliable feeding on cable runs over 3 metres. Use non-metallic (Teflon or nylon) liners. See our article on feedability in aluminium MIG welding
  • Travel speed — higher travel speeds than steel are typically required to prevent heat build-up and burn-through on thin aluminium. Move faster than feels instinctive
  • TIG on aluminium — use 100% argon and a 2% cerium-alloyed (or pure) tungsten electrode, small diameter. AC current is required for aluminium TIG to provide the oxide-cleaning action of the positive half-cycle

For troubleshooting aluminium MIG problems, see our article on aluminium MIG troubleshooting at the arc.

Welding Galvanised Steel

Galvanised steel presents a particular challenge: the zinc coating is not compatible with the welding process and typically produces welds with porosity and poor bead appearance as the zinc vapourises ahead of the arc. It also generates zinc fume — a serious health hazard that requires effective local exhaust ventilation and respiratory protection. Never weld galvanised steel without appropriate fume extraction.

  • Process — MIG with higher CO₂ content shielding gas (75% Ar / 25% CO₂) helps with the cleaning action on the zinc-contaminated surface. Slightly higher voltage and slower travel speed than for equivalent thickness bare steel give the weld pool more time to de-gas and the toes to tie in smoothly
  • Dual-shield flux-cored wire — an alternative worth considering for galvanised steel. The dual shielding mechanism (inner flux slag + external shielding gas) provides two cleaning actions, which can produce better bead appearance and fewer porosity issues than solid wire alone on heavily galvanised material. See our flux-cored wire guide
  • Fume control — zinc fume causes metal fume fever with short-term overexposure, and serious longer-term health effects with repeated exposure. Ensure source extraction is in place and that respiratory protection is worn where extraction cannot adequately control fume levels

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Frequently Asked Questions

One of the most common challenges is preventing burn-through, which occurs when excessive heat melts completely through the base metal. Thin materials absorb heat quickly and can easily become distorted or damaged. Using the proper welding process, reducing heat input, and maintaining consistent travel speed can help produce cleaner, stronger welds.

Several welding processes can be used successfully on thin materials, but MIG and TIG welding are among the most common. TIG welding offers excellent control and precision, making it ideal for very thin materials and high-quality applications. MIG welding can also work well on thin metal when paired with the appropriate wire size and machine settings, especially for production environments.

Warping is often caused by excessive heat buildup during welding. To minimize distortion, welders can use lower amperage settings, make shorter weld passes, alternate weld locations, and allow the material to cool between passes when necessary. Proper fit-up and clamping techniques can also help maintain alignment and reduce movement during the welding process.