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Stress corrosion cracking of 304L vs. 316

2004

I would like to know about the possibilities of stress-corrosion cracking for SS 304L at following thermal hydraulic conditions:

1. Temperature = 150 deg.centigrade - tube side
2. Chloride presence = 150-160 ppm
3. Service: oil carry over problem with the service gas(which is non corrosive).

Pls. let me know, whether I could use this material or should go for 316SS.

Thanks
Osama

Osama Syed
fertlizer company - Rawalpindi, Punjab, Pakistan

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First of two simultaneous responses -- 2004

No significant difference is susceptibility to SCC between those two grades. If you think SCC might be a problem, you should consider 2205 - more expensive initially, but a whole lot cheaper in the long run when you don't have to replace or repair it.

Bill Reynolds [deceased]
consultant metallurgist - Ballarat, Victoria, Australia
We sadly relate the news that Bill passed away on Jan. 29, 2010.

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Second of two simultaneous responses -- 2004

Two of the criteria for SCC in stainless steel have been met - temperature over 50, and presence of Chlorides. You don't say if you have already experienced problems, but in my experience you are likely to. I presume the environment is wet - ?

Unfortunately 304 and 316 are both susceptible, 316 with better pitting resistance from 2+% Molybdenum is better (usually) as it can prevent pit initiation.

In our application, we aim to keep Chlorides as low as possible, and reduce stresses as far as possible, with a regular inspection regime to keep failure incidence low.

Best of Luck

Martin Rich
ship repair - Plymouth, UK