Analysis of stress corrosion cracking process of austenitic stainless steel SUS304 in 30%MgCl_2 aqueous solution by electrochemical noise method

摘要

Electrochemical noise was measured during SCC tests in order to apply an electrochemical noise method to monitor stress corrosion cracking of SUS304 steel made component in actual chemical plants. SCC tests were conducted for sensitized SUS304 steel specimen in 30 wt% MgCl_2 aqueous solution at 353 K by use of SSRT testing apparatus. Commercial SUS304 steel was used for current counter electrode and comparative potential electrode in an electrochemical noise measurement (ENM) system. It was observed that at low stress range corrosion pits initiated and propagated on specimen surface. Then crack initiated from corrosion pit and propagated to final failure. When pit initiates, electric potential of the specimen increased. When crack propagates from corrosion pit electric potential reached to a level over 0 mV. It was also observed that current value increased in crack propagation process. It can be predicted to calculate crack initiation time from the relationship between stress and ENM data. It can be concluded that stress corrosion cracking process can be monitored by use of ENM system.