Effect of Capillary Water on Electrochemical Corrosion Behaviour and Mechanism of X70 Steel in Silty Clay

In this paper, we simulated a corrosive environment with dynamically changing capillary water wetting fronts in silty clay by indoor simulation tests and studied the electrochemical corrosion behaviour of X70 steel in the corrosive environment with rising capillary water at different ages by electrochemical means. The results show that the electrochemical corrosion behaviour of X70 steel in silty clay is significantly influenced by changes in the capillary water wetting front. The equivalent circuit model for the electrochemical corrosion of X70 steel is a dynamic process that changes with the position of the capillary water wetting front. The polarization resistance R-p of X70 steel at position 1# of the soil column shows a pattern of decreasing and then increasing with increasing burial time, while the polarization resistance R-p of X70 steel at position 2# of the soil column shows a pattern that roughly increases gradually with increasing burial time. The polarization resistance R-p of X70 steel at the position of the capillary water wetting front decreases significantly, the cathodic branch of the polarization curve shifts significantly to the right, and the corrosion rate increases dramatically. At the same time, the ions in the soil with the rise of capillary water to the upper part of the soil column will also lead to a significant reduction of the upper X70 steel polarization resistance R-p and a sharp increase of the corrosion rate. In addition, the presence of clay particles has a catalytic effect on the cathodic reaction of X70 steel, an effect that is more pronounced when the X70 steel is in the TPB region.