Metallurgical aspects of rock bolt stress corrosion cracking

This paper reports on the metallurgical influence on rock bolt stress corrosion cracking for a range of: (1) existing rock bolt steels and (2) commercial steels. Rock bolt steels 1355, MAC and MA840B displayed SCC when loaded at 0.019 MPa s−1 in the sulphate pH 2.1 solutions at the free corrosion potential. They had comparable threshold stresses and comparable stress corrosion crack velocities. Rock bolts steel 5152CW10D had the best SCC resistance of the rock bolt steels tested. Cold work increased the resistance of 5152 to SCC. The five commercial steels 1008, X65, X70, 4140 and 4145H were subjected to the linearly increasing stress test (LIST) in the dilute pH 2.1 sulphate solution at their free corrosion potential and at increasingly negative applied potential values to −1500 mV. The increasingly negative applied potential increases the aggressivity of SCC conditions because of increasing hydrogen liberated at the specimen surface. The steels 1008, X65, X70 and 4145H resisted SCC for all applied potentials including −1500 mV.