Research on Dynamic Alternating Current Corrosion Behavior of X65 Pipeline Steel Under Cathodic Protection

An indoor corrosion simulation experiment device was built to explore the influence of dynamic alternating current (AC) interference on the corrosion behavior of pipeline steel under different cathodic protection (CP) levels. When the interference time in each interference cycle is 350 s, the dynamic AC corrosion rate was comparable to the steady AC corrosion rate. For JAC of 30 A/m(2), the corrosion rate of the specimen can be controlled below 0.0254 mm/y when the CP current density is higher than 0.06 A/m(2). As JAC is greater than or equal to 100 A/m(2), with the increase of the CP current density, the corrosion rate of the specimens decreased first, then increased and decreased again. In this paper, the real-time AC/DC potential on the surface of the specimen is monitored, combined with the Pourbaix diagram and the evolution of corrosion product film. The dynamic AC corrosion mechanism under different CP levels was explored.