Effect of Capillarity in Unsaturated Silty Clay on Electrochemical Corrosion Behavior of X70 Steel

Abstract

Purposes It is important to explore the law of capillary action on the corrosion of X70 steel in soil. Methods On the basis of the theory of unsaturated soil and electrochemical impedance spectroscopy, combined with polarization curve technology, electrochemical impedance technology, scanning electron microscopy, and other test methods, the electrochemical corrosion behavior of X70 steel caused by capillarity in silty clay was investigated through the simulation test of one-dimensional soil column instrument under indoor conditions. Findings The test results show that capillary action has a certain influence on the electrochemical corrosion behavior of X70 steel, that is, the corrosion rates of steel sheet at the height of 12 and 27 cm of soil column first increase and then decrease with embedding time, and the corrosion rate of steel sheet at the height of 42 and 57 cm of soil column first decrease and then increase with embedding time; The rising rate of capillary water in silty clay meets the law of being first fast and then slow. Conclusions The corrosion type of X70 steel sheet surface is mainly pitting corrosion, and the corrosion product surface is accompanied by deep and wide cracks. With the increase of soil sample height, the corrosion degree decreases, and the size and number of corrosion pits show a decreasing trend on the whole. In the rising process of capillary water, when X70 steel sheet is at the solid-liquid-gas three-phase boundary, its corrosion rate is the fastest and the corrosion degree is the most serious.

Keywords

• unsaturated silty clay
• x70 steel
• capillary action
• electrochemical impedance spectroscopy
• sem