Cathodic Protection Criterion Applicability of X80 Steel with Alternating Current Interference in Alkaline Solution

The corrosion characteristics of X80 steel in 0.5 mol/L NaHCO3 solution under the condition of different alternating current (AC) densities with the -850 mV (CSE) cathodic protection criterion was studied by polarization curves, electrochemical impedance spectroscopy(EIS) and SEM. The results show that when the cathodic Tafel slope was greater than the anodic Tafel slope, X80 steel AC current corrosion was lighter, when the cathodic Tafel slope was less than the anodic Tafel slope, the steel was bound to an AC current corrosion. With the increase of AC density, the corrosion product film resistance and the charge transfer resistance exhibited fluctuation, but the general trend was decrease, indicating that X80 steel suffered corrosion constantly. Finally the alternating current corrosion protection scope under the cathodic protection criteria was determined.