Corrosion Behavior of Q235 Steel Exposed in Deepwater of South China Sea

For the first time, the corrosion behavior of Q235 steel in 1200, 2000 and 3000 m deepwater of South China Sea for 0.5 year was reported in this study. The corrosion morphology and corrosion products properties were investigated using different techniques, such as 3D optical microscope, scanning electron microscope, x-ray diffraction analyzer and electrochemical impedance spectroscopy. The main environmental factors influencing the corrosion rate of Q235 in deep sea were discussed by applying gray relational analysis. The results indicated that uniform thinning occurred after exposure. A large number of tiny pits were distributed under the corrosion products with a two-layer structure. The corrosion rate and average pitting depth of samples exposed at 2000 m were lower than those exposed at 1200 and 3000 m, and the main environmental factors determining the variation of corrosion rate at different depths were temperature and dissolved oxygen concentration. Hydrostatic pressure had slight effect on the corrosion rate of Q235 steel, but promoted the formation of a more uniform corrosion morphology.