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AUTO PASSIVATION ON TIG WELDS OF STAINLESS STEELS

I AM INTERESTED TO KNOW IF AUTO PASSIVATION OCCURS ON WELDS OF AUSTENITIC STAINLESS STEELS WELDED WITH GAS TUNGSTEN ARC WELDING. HOW MANY DAYS IT TAKES FOR AUTO PASSIVATION. WHAT GRADES OF STAINLESS STEELS ARE GOOD FOR AUTO PASSIVATION AFTER WELDING.

Dr K G K MURTI
- TIRUCHIRAPPALLI, TAMILNADU, INDIA
2002

2002

Mr. Murti,

I don't fully understand your question or purpose. Passivation is really an oxidation process that forms a layer of chromium and/or nickel oxides on stainless steels. Argon in TIG welding expels oxygen during welding but as soon as it is shut off the weld surface will be exposed to oxygen and if still hot will passivate very quickly (matter of seconds-minutes not days I would say). This natural phenomena will not produce a high quality, uniform and good looking passivation layer. Now, what is your question about grades of SS to autopassivate? Do you intend to avoid an engineering process? Please explain your problem better.

Guillermo Marrufo
Monterrey, NL, Mexico

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