27.10.2021 •

Experimental Study on the Corrosion Behavior of X70 Steel Under Asymmetric Dynamic DC Interference


The corrosion behavior of X70 steel in simulated soil environment under asymmetric dynamic direct current (DC) interference was studied by immersion tests. The experimental results showed that the negatively asymmetric dynamic DC interference would induce localized corrosion. Under the same dynamic period of 160 ±80 s, when the negative half-wave current density remained stable at −10 mA/cm2 and the positive half-wave one decreased from 7 to 1 mA/cm2, the equivalent diameters of the localized corrosion zones became smaller and the steel samples demonstrated typical pitting corrosion morphologies. To further explore the effect of asymmetric dynamic DC interference on the localized corrosion behavior of carbon steel, a variety of experimental measurements were carried out including real-time DC potential monitoring, in-situ near-surface pH measurements, cyclic voltammetry, and Mott–Schottky tests. It was found that the localized corrosion behavior was probably related to the breakdown of passive film formed on the metal surface exposed to negatively asymmetric DC current generated high pH conditions.