CORROSION BEHAVIOR OF X70 PIPELINE STEEL IN SIMULATED KUERLE SOIL SOLUTION WITH CO2

The effect of CO2 on the stress corrosion cracking (SCC) behavior of X70 pipeline steel in simulated Ku'erle soil solution was investigated by polarization curve, EIS and slow strain rate testing (SSRT). The morphologies of fracture surface of X70 pipeline steel in the solution with the different partial pressures of CO2 were analyzed by SEM. The results show that the dissolved CO2 reacted with the corrosion product of FeCO3 and a dissolved complex (Fe(CO3)2 2-) is formed. The cathodic regime representing evolution of hydrogen is also affected by the presence of dissolved CO2. The SCC of X70 pipeline steel in dissolved CO2 solution follows the mechanism of hydrogen-facilitated dissolution. As the increase of the pressure of CO2 in the solution, the effect of hydrogen induced cracking is enhanced.