Investigation of Marine Atmospheric Corrosion of a New Developed Low Carbon Bainitic Steel

      A low carbon bainitic steel with yield strength higher than 780MPa has been developed for future application in marine environment. Corrosion behaviors of the steel exposed in two typical marine atmospheres were investigated, one in Qingdao, a representative of temperate zone marine environment with industry contamination on the east coast of China, as well as another one in Wanning, a representative of subtropical marine environment on Hainan Island in southern China.      Corrosion rate was determined by thickness loss of the steel, and the rust formed on the steel surface during atmospheric exposure was analyzed by XRD, N₂ adsorption approach and SEM. Investigations indicate that the steel corroded more severely in Wanning than in Qingdao. The rust formed in Wanning contained more β-FeOOH, γ-FeOOH and Fe₃O₄ and exhibited higher porosity and lower resistance to chloride ions permeation than that in Qingdao. The effect of thermal shock on the integrity of the rust layer was evaluated by indentation-quench test. The results showed that thermal shock could induce crack expansion in the rust layer, at the same time, the interface between the rust layer and steel exhibited higher resistance to thermal shock than the rust layer.