Abstract
Extensive research was conducted on prestressed ASTM A648 Class II steel wire to identify the fracture morphology. Hydrogen embrittlement results when this prestressed steel wire, embedded in concrete cylinder pipe, is cathodically overprotected. From this study, a correlation was established between the environmental variables (pH, cathodic potential) and the type of failure. These experiments demonstrated that hydrogen embrittlement occurred in both environments (pH 2 and pH 12) and affected the fracture behavior of the wires. The wires subjected to cathodic potentials above –1.2 VSCE showed more susceptibility to hydrogen embrittlement than the other samples. The SEM fractographic analyses showed a specific fracture morphology for the hydrogen embrittled regions of the charged samples. The SEM analysis of the fracture surface showed a thin rim (about 20-50 microns in thickness) on the outer surface that contrasts with the rest of the fracture morphology. In summary, the ASTM A648 steel prestressed wire showed high susceptibility to hydrogen embrittlement at cathodic potentials above –1.2 VSCE, resulting in severe loss of toughness and catastrophic failure under sudden action of force (water hammering). Therefore, it is extremely important to avoid overprotecting these prestressed wires when using a cathodic protection system to improve life expectancy.
