Laboratory-based coupon testing for the understanding of SCC in rockbolts

Abstract

Coupon testing has been used extensively to understand the effects of general corrosion on engineering materials within their operational environment. This study examined the use of various coupon specimens to examine stress corrosion cracking (SCC) of rockbolts in the underground mining environment. The standard ASTM G39 bend beam SCC specimen, as well as a pin-loaded slotted specimen, was used in this investigation. It was identified that the critical stress threshold for HSAC 840 rockbolt steel is approximately 580 MPa, slightly lower than the material’s yield strength. It was shown that the higher toughness HSAC 840 grade rockbolt steel performed better than AISI 1355 grade rockbolt steel, emphasising the importance of steel chemistry. It was also found that galvanising improved SCC resistance but shot peening reduced SCC resistance.