Oxygen-concentration cell induced corrosion of E690 steel for ocean platform

In order to investigate the corrosion resistance of ocean platform steel E690 in sea water, the corrosion induced by oxygen-concentration cell of E690 steel in 3.5% NaCl with oxygen concentration within a range of 0.3 to 8 mg/L was investigated by means of electrochemical measurement techniques, scanning electron microscopy and Raman spectroscopy. The influence of the difference in dissolved oxygen, the ratio of cathode area to anode area and the corrosion product on the corrosion behavior of E690 steel was examined respectively. It was found that: when the ratio of cathode area to anode area was less than four (S_c/a≤4), the cathode and these ratios would be the main factor that influenced the oxygenconcentration cell corrosion; when S_c/a>4, the dissolved oxygen would be the main factor that influenced the oxygen-concentration cell corrosion; How the corrosion product influenced the oxygen-concentration cell corrosion depends on the dissloved oxygen. When the rusted metal under an oxygen-deficient condition, the rust layer would prevent the substrate from corrosion; when the rusted metal was immersed in an aerated condition, the corrosion product would participate in the cathodic reaction process, which would accelerate the anode dissolution and resulted in localized corrosion, such as pitting.