Effect of Capillary Action on Short Term Electrochemical Corrosion Behaviour of X70 Steel in Unsaturated Saline Soil

Abstract

In this study, electrochemical impedance spectroscopy (EIS) was used to analyse the short-term corrosion of X70 steel in four soil corrosion systems with different NaCl content affected by capillary water. The results showed that the short-term electrochemical corrosion behaviour of X70 steel in saline soil was significantly affected by capillary water. In a soil corrosion system with NaCl content of less than or equal to 1.0%, the polarization resistance RP of X70 steel at position 1# was generally less than that at position 2#, and the corrosion rate of X70 steel at position 1# was greater. SEM results showed that the degree of corrosion pit ulcer on the surface of X70 steel at position 1# was generally greater than that at position 2# in the soil with a NaCl content less than or equal to 1.0%. In addition, the equivalent circuits of X70 steel at positions 1#, 2# were Rs(C1R1(WRctQ)) and Rs(WRctQ), respectively, by fitting the EIS results. The impact of the capillary water upturn on the corrosion of X70 steel was further determined by analysing the equivalent circuit parameters and EDS results.