Successful TIG welding of stainless steel depends on clean preparation, the correct filler rod and — critically — back purging to protect the rear of the weld with Argon. Without purging, oxygen causes heavy oxidation known as “sugaring”, which reduces corrosion resistance and weakens the weld. This is essential for pipework, food processing and pharmaceutical applications.
Why should you purge stainless steel?
Back purging protects the rear of the weld with Argon during TIG welding. Without purging, oxygen causes heavy oxidation, commonly known as “sugaring”, which reduces corrosion resistance and weakens the weld. Back purging is essential for pipework, food processing and pharmaceutical applications.
What is sugaring in stainless steel welding?
Sugaring is severe oxidation on the rear of a stainless steel weld caused by insufficient shielding gas. The rough oxide layer reduces corrosion resistance and may lead to contamination in hygienic applications. Using a proper purge system prevents sugaring and produces clean, corrosion-resistant welds.
What is heat tint?
Heat tint is the coloured oxide layer that forms on stainless steel after welding. The colours indicate different oxidation levels caused by heat exposure. Removing heat tint through pickling or mechanical cleaning helps restore corrosion resistance where required.
Can you weld stainless steel to mild steel with TIG?
Yes. Stainless steel can be welded to mild steel using 309L TIG rods, which are specifically designed for dissimilar metal welding. 309L accommodates differences in chemical composition and thermal expansion, producing strong and reliable welds. See our TIG filler rod selection guide for how 309L compares with 308L and 316L.
How do you TIG weld food-grade stainless steel?
Food-grade stainless steel requires clean preparation, correct filler rods, adequate purging and careful heat control. Welds should be smooth, fully penetrated and free from contamination. Proper finishing is essential to maintain hygiene and corrosion resistance. This is one reason TIG is the preferred process in food manufacturing.
How do you TIG weld pharmaceutical pipework?
Pharmaceutical pipework requires high-quality orbital or manual TIG welding with full Argon purging to ensure clean internal welds. Correct filler metal, controlled heat input and strict cleanliness are essential to meet hygienic standards.
How do you TIG weld duplex stainless steel?
Duplex stainless steel requires specialist filler rods, controlled heat input and careful shielding gas selection to maintain the correct balance between ferrite and austenite. Following approved welding procedures is essential for preserving corrosion resistance and strength.
The right consumables for clean stainless welds
Clean, corrosion-resistant stainless steel welds come down to the right filler rod, the right shielding and a proper purge set-up. Weldability SIF supplies stainless TIG filler rods and purging accessories, and our technical team can advise on the correct consumables for hygienic and pipework applications — get in touch.