Stainless steel — commonly called inox in the Swiss and continental European industry, Edelstahl in German — is the material of the food industry. From conveyors to frames, tanks to pipework: wherever food is processed, chromium-nickel steel dominates. The joining technique between these components determines hygiene, durability, and ultimately food safety. And this is where it gets challenging: TIG welding on stainless steel in Swiss food environments requires expertise that goes far beyond standard craftsmanship.
Why TIG welding is the standard
In food production, TIG welding (Tungsten Inert Gas, known as WIG in German) has established itself as the reference process — for good reasons:
Clean weld seam: TIG produces smooth, porosity-free weld seams with minimal spatter. This is critical because every pore and every spatter is a potential source of contamination.
Precise heat input: Exact heat control prevents excessive heat tint and reduces distortion — particularly important on thin-walled stainless steel tubes and sheets.
Shielding gas coverage: Argon as shielding gas prevents oxidation during welding. With correct application, a uniform, chromium-rich passive layer forms on the weld.
Purge gas: For high-quality joints in the food sector, the weld root is additionally protected with purge gas (argon or argon/hydrogen mix). Without root protection, heat tint and oxide layers form inside, drastically reducing corrosion resistance.
The right materials
Not every stainless steel is suitable for the food industry:
AISI 304 (1.4301)
The standard material for most food production applications. Good corrosion resistance against most organic acids and neutral cleaning agents. Economical and easy to fabricate.
Application: Frames, conveyor structures, covers, tanks for non-aggressive media.
AISI 316L (1.4404)
The better choice when in contact with chlorinated cleaning agents, salt solutions, or acidic media. The “L” stands for Low Carbon (max. 0.03% C) — reducing the risk of intergranular corrosion after welding.
Application: Wet processing areas, meat processing, dairy technology, CIP piping systems.
Duplex steels (e.g. 1.4462)
For particularly aggressive environments or when high mechanical strength is required. Rather rare in the Swiss food industry but common in the beverage sector.
Surface finish: the weld must be cleanable
The weld seam must have the same surface finish as the surrounding area. In the food industry, the following guideline values apply:
- Ra ≤ 0.8 µm: Standard for product-contact surfaces (EHEDG recommendation)
- Ra ≤ 1.6 µm: Acceptable for non-product-contact surfaces in cleaning zones
- Ra ≤ 3.2 µm: Only for areas without food contact and without regular wet cleaning
In practice, this means: after welding, the seam must be post-processed. Depending on requirements:
- Brushing: Removes heat tint, achieves Ra approx. 1.0–1.6 µm
- Grinding: Multiple grit stages (80 → 120 → 240) for Ra ≤ 0.8 µm
- Pickling and passivation: Chemical post-treatment that restores the chromium oxide layer
- Electropolishing: For the highest requirements (pharma, baby food) — achieves Ra ≤ 0.4 µm
Common mistakes in stainless steel welding
1. Heat tint not removed
The colourful iridescent heat tint near the weld seam looks harmless but is a problem: it indicates a destroyed passive layer. Pitting corrosion starts beneath these discolourations — especially with chlorinated cleaners.
2. Iron contamination
Tools previously used on carbon steel (grinding discs, brushes, support tables) transfer iron particles to the stainless steel. These particles rust.
Solution: Use dedicated tools for stainless steel. No cutting discs or brushes made of carbon steel.
3. Insufficient shielding gas
Insufficient argon flow, leaking hoses, or missing root protection — all lead to oxidation and poor weld quality.
4. Excessive heat input
Stainless steel has poor thermal conductivity. Too much heat causes distortion, grain coarsening, and sensitisation.
Solution: Limit heat input, interpass temperature ≤ 150°C.
Our approach
Our welders have years of experience in stainless steel welding in the food industry — directly on site:
- Certified procedures: Welder qualification per EN ISO 9606-1
- On-site work: We weld where the plant is — under real production conditions
- Complete service: From cutting to welding to surface treatment, all from one source
- Documentation: Welding protocol with parameters, material certificates, and photo documentation
Conclusion
Stainless steel welding in the food industry is more than joining metal — it is hygiene engineering. The right material choice, clean TIG welds, correct surface treatment, and contamination prevention determine whether a welded joint functions reliably for years or becomes a hygiene risk.
Need professional stainless steel welding in your plant? +41 32 552 28 88 or info@vldservice.ch.
