Hydrogen-related stress corrosion cracking in line pipe steel

A correlation between hydrogen concentration (C-0) and the critical stress intensity factor for propagation of hydrogen-related cracks (K-ISCC) has been established by fracture mechanics testing of compact tension, CT, specimens for the heat affected zone (HAZ) of an API 5L X70 pipeline steel. The correlation can be expressed as K-ISSC = 89 exp(-0.09C(0)). In turn, the hydrogen concentrations resulting from cathodic protection (CP) of steel exposed in a clay sediment and a peat bog have been assessed using a recently developed hydrogen sensor based on the Arup type. A comparison of the fracture mechanics test results and the hydrogen concentrations assessed by field measurements in the clay and in the peat bog indicates that no critical hydrogen concentrations can be generated by CP in these sediments.