The fracture toughness of CO2 corrosion scale in pipeline steel

The fracture toughness of CO2 corrosion scale in X65 pipeline steel has been measured using Vicker's indentation on a polished cross-section of the scale and the variation of the fracture toughness with scale forming temperature has been investigated. The results show that CO2 corrosion scale formed at 65 °C to 90 °C is (Fe,Ca)CO3 and that at 115 °C is (Fe,Ca,Mg)CO3, respectively. The scale thickness decreases and the amount of Ca in the scale increases with increasing scale forming temperature. The fracture toughnesses of the outer and inner layers of the scale formed at 65 °C are 0.68 MPam1/2 and 1.46 MPam1/2, respectively. The fracture toughness of the CO2 corrosion scale decreases with increasing scale forming temperature.