"corrosion of stainless steel after stress relief"

Question:

"Upon inspection of a stainless steel tank (steel grade 316L), my company has noted rusting/corrosion on the tank exterior. We believe that this is the result of sensitization from previously conducted heat treatment for stress relief. It is my understanding that such treatments may result in chromium depletion, making the steel surface susceptible to rust and corrosion. Is this correct? If you could recommend sources of information on the effects of rusting and sensitization on the structural integrity and life expectancy of stainless steel tanks, it would be greatly appreciated."

Answer:

Sensitization is the result of heating unstabilized austenitic stainless steels to between ~800-1600F. This treatment results in chromium carbide formation at grain boundaries, depleting the adjacent material in chromium. It can result in accelerated corrosion in certain aqueous environments. It should not affect the 316SS tank O.D. However, depending on the tank contents, it may influence corrosion of the I.D. For materials discussing sensitization, you could contact NACE International at 281-228-6200.

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