Macro-cell Corrosion of X70 Steel Between Salinized Soil and Seawater

The macro-cell corrosion of X70 steel between salinized soil and seawater was studied by electrochemical impedance spectroscopy(EIS). It was found that the X70 steel in seawater was corroded as the anode, the corrosion rate was 25.3 times of the natural corrosion rate and the corrosion process was controlled by cathodic reaction. As a result of the effects of both corrosion product membrane and chlorine ion, the macro-cell corrosion rate reduced firstly, then increased quickly, and reduced slightly to a steady state at last. The results also showed that the electromotive force (EMF) of the macro-cell performed differently from the conventional macro-cell corrosion in soils. Because of the effect of polarization resistance, EMF first reduced slightly, then increased quickly and stabilized.