Abstract:

The electrochemical corrosion behavior of X80 pipeline steel was investigated in northern Shaanxi saline soil saturated with water by using electrochemical measurement, scanning electron microscopy (SEM) and energy dispersive spectrum (EDS)analysis.The results showed that the corrosion tendency and corrosion rate of X80 steel significantly increased，pitting depth and area increased continuously, which was induced by change of corrosion morphology from uniform corrosion to localized corrosion. Corrosion mechanism was oxygen-concentration corrosion cell and localized corrosion autocatalysis effect, and corrosion rate was controlled by oxygen diffusion process.The characteristics of double capacitive reactance arcs and Warburg impedance could be found in electrochemical impedance spectra, the resistance of charge transfer and diffusion mass transfer in pitting became bigger and bigger, and binding layer resistance significantly decreased.It was dependent on the integrity and compactness of corrosion product films.The corrosion product was basically a mixture of iron oxides, iron sulfides and salts in soil.