Stress corrosion cracking of duplex stainless steel under evaporative conditions

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Stress corrosion cracking of duplex stainless steel under evaporative conditions

Hinds, Gareth / Turnbull, Alan

The susceptibility of 22Cr and 25Cr duplex stainless steels to stress corrosion cracking under evaporative seawater conditions has been evaluated using a modified drop evaporation test. At an applied stress of 90% sigma(0.2) a threshold temperature for cracking of around 70 deg C was identified for both materials. Observation of patchy corrosion and occasional pitting beneath the salt layer was consistent with an aggressive underdeposit chemistry but there was also indication that the extent of corrosion was enhanced by the applied stress. No cracking was observed below the proportional limit in the stress-strain curve at 100 deg C, suggesting that a combination of this chemistry and micro-plastic deformation is responsible for cracking of the steels. The engineering implication is that existing recommendations for the critical temperature for coating of duplex stainless steel to avoid failures in service may need to be revised downwards.