Effect of dissolved oxygen on pitting corrosion behavior of low-alloy steel under hydrostatic pressure

Abstract

Effect of dissolved oxygen on pitting corrosion behavior of low-alloy steel under hydrostatic pressure in neutral 3.5 wt.% NaCl solution was investigated by scanning electron microscope (SEM), 3-D measuring microscope and so on. The results show that the combined effect of hydrostatic pressure and dissolved oxygen increases the overall growing rate of corrosion pits and causes deeper corrosion pits but decreases their sizes in the horizontal direction. Electrochemical measurement results reveal that dissolved oxygen dominate the corrosion kinetics of low-alloy steel in the environment containing high hydrostatic pressure and high dissolved oxygen by accelerating cathodic process, slowing down the anodic process and promoting open circuit potential (OCP). Consequently, the increased charge transfer process makes the pits have a larger volume and depth. Meanwhile, the decreased initial potential energy difference based on energy theory calculation at the initiation site by dissolved oxygen possibly inhibits the pitting growth in the horizontal direction.