TIG vs MIG Welding for Aluminum Cases: Which Is Right for Your

A robotics company in Munich was ordering a batch of 30 field cases for their portable inspection robots. The cases needed to be structurally rigid enough to survive being carried over rough terrain, but also light enough for one technician to carry. They sent the drawing to two shops. Shop A quoted MIG welding at $85 per case. Shop B quoted TIG welding at $140 per case. The buyer went with Shop A — $55 savings per case, $1,650 total savings. Six months later, 8 of the 30 cases had cracked welds at the handle mounting points. The welds were brittle, had porosity, and cracked under repeated impact. Replacement and repair cost $4,800. Plus, three field robots were delayed while their cases were repaired. The $1,650 “savings” cost nearly $10,000.

TIG vs MIG welding is one of the most common questions in custom aluminum case manufacturing. The answer isn’t “TIG is better” or “MIG is cheaper” — it depends on what the case needs to do, how it’s built, and what failure mode you’re trying to prevent. This guide breaks down the two processes, where each makes sense, and how to choose based on your actual requirements.

What’s the Difference, Mechanically

TIG (GTAW — Gas Tungsten Arc Welding)

Tungsten Inert Gas welding uses a non-consumable tungsten electrode to create the arc. Filler metal is fed in by hand (or not at all for thin sections). The weld pool is protected by argon gas. TIG is slow, precise, and requires a skilled welder.

• Weld quality — Clean, consistent, low porosity. The welder controls the heat input precisely, so there’s less distortion and less burn-through on thin aluminum
• Appearance — Smooth, ripple-free weld beads. Looks professional and is easy to inspect visually
• Speed — Slow. A TIG welder lays down about 100-150mm of weld per minute on 3mm aluminum. MIG does 300-500mm per minute
• Cost — Higher labor cost (skilled welder, slower process). But lower rework cost because there’s less distortion and fewer defects
• Best for — Thin aluminum (1.5-3mm), visible welds, precision assemblies, cosmetic cases, aerospace and medical applications

MIG (GMAW — Gas Metal Arc Welding)

Metal Inert Gas welding uses a consumable wire electrode that feeds automatically through the torch. The weld pool is protected by argon or argon/CO₂ mix. MIG is faster, more forgiving, and requires less operator skill.

• Weld quality — Good but not as clean as TIG. More spatter, more porosity, more heat input. On thin aluminum, MIG can burn through or warp the panel
• Appearance — Rougher weld bead with visible ripples and spatter marks. Usually needs grinding or filing to look clean
• Speed — Fast. MIG lays down 300-500mm per minute on 3-5mm aluminum. It’s 3-4x faster than TIG
• Cost — Lower labor cost (faster, less skilled welder). But higher rework cost because of distortion, spatter cleanup, and potential porosity
• Best for — Thicker aluminum (4-8mm), structural frames, hidden welds, high-volume production, applications where appearance doesn’t matter

Where Each Process Makes Sense for Cases

Use TIG When:

• The case is thin (2-4mm panels) — MIG will burn through or warp thin panels. TIG controls heat input precisely
• The weld is visible — If the weld shows on the outside of the case, TIG gives a clean, professional appearance that doesn’t need grinding
• The case carries high-value equipment — A cracked weld on a $50,000 instrument case is a $10,000 repair. TIG’s lower defect rate is worth the premium
• The case sees repeated impact or vibration — TIG welds are more ductile and less prone to brittle fracture under cyclic loading. MIG welds with porosity act as crack initiation points
• The case needs to be sealed (IP rated) — TIG welds are more consistent, which means the gasket surface is flatter and the seal is more reliable. Porous MIG welds can leak air and moisture

Use MIG When:

• The case is thick (5-8mm panels) — MIG handles thick sections better because it deposits more metal per pass and has deeper penetration
• The weld is hidden — If the weld is inside the case or covered by a corner protector, the appearance doesn’t matter. MIG’s speed wins
• The case is a heavy-duty flight case with a welded frame — The frame welds are structural, not cosmetic. MIG’s faster deposition rate is efficient for frame building. The frame gets powder-coated anyway, so spatter doesn’t matter
• You’re building in volume — For runs of 100+ cases, the labor savings from MIG add up. As long as the welds are structurally adequate and not visible, MIG is cost-effective
• The cost is the primary driver — If the equipment inside is under $2,000 and the case is a simple transport box, MIG at $85 per case is reasonable. The risk of weld failure is acceptable relative to the equipment value

Weld Defects: What to Look For

Whether you specify TIG or MIG, you need to know what a good weld looks like and what a bad one looks like:

Porosity

Tiny gas bubbles trapped in the weld. Looks like pinholes on the surface or small voids inside. Porosity weakens the weld and is a common MIG defect on aluminum (especially if the material is dirty or the gas flow is off). A TIG welder who takes his time will clean the material and use proper gas coverage, so porosity is rare.

Burn-through

The weld pool melts through the panel, leaving a hole. This happens with MIG on thin aluminum when the travel speed is too slow or the current is too high. TIG is less prone to burn-through because the heat input is more controllable.

Undercut

A groove along the weld toe where the panel has been melted away but not filled. Undercut creates a stress concentration and is a common crack initiation point. It’s usually a sign of too much current or incorrect travel speed.

Distortion

The panel warps as the weld cools and contracts. More of a problem with MIG because the heat input is higher and more concentrated. TIG’s lower heat input means less distortion. Distortion affects flatness, which affects gasket sealing.

What We Specify

For our custom case line, we use TIG welding for:

• All cases with 3-4mm 5052 aluminum panels (our standard instrument case thickness)
• All cases where the weld is visible on the exterior
• All cases carrying equipment over $5,000 in value
• All IP-rated cases (gasket sealing requires flat panels)

We use MIG welding for:

• Heavy-duty flight cases with 5-6mm welded frames (the frame is structural, the aluminum skin is riveted on)
• Cases where the weld is internal or covered by hardware
• High-volume runs (100+) where the cost savings are significant and the equipment value is lower

The choice isn’t about which process is “better” — it’s about matching the process to the application. TIG costs more per weld but eliminates rework, porosity, and distortion on the panels that matter. MIG is fast and cheap for structural frames that won’t be seen. When you’re quoting a custom case, ask which process the shop uses on which parts — and make sure the answer matches what your equipment needs.