Corrosion behaviour investigation of 460 low alloy steels exposed in the natural deep-sea environment

The corrosion behaviours of 460 low alloy steels were investigated by the field exposure corrosion experiments with various long periods and 1200-3000 m depths in the natural deep-sea environment. XRD analysis results indicate that corrosion products of beta-FeOOH, gamma-FeOOH and Fe3O4 increase and the corrosion product of alpha-FeOOH decreases with the exposure sea depth extending. Electrochemical experiment results reveal the corrosion status is aggravated with the exposure sea depth extending: corrosion potentials shift negatively to a minimum self-corrosion potential of -0.590 V (vs. SCE) and charge transfer resistances decrease to a minimum of 278 omega cm(2). Corrosion behaviours analysis shows that the average corrosion rate decreases with the time increasing and reaches a maximum value of 101 mu m a(-1). The maximum pitting depth varies between 63.0 mu m and 138 mu m. Gray relational analysis shows that the corrosion rate of 460 steel is most influenced by the pressure and dissolved oxygen concentration of deep sea, exhibiting a positive correlation relationship.