Corrosion Behavior and Mechanism of 907A Low Alloy Steel in Simulated Deep Sea Environment

The corrosion behavior of 907A low alloy steel in simulated 1 000 m deep sea environment was studied by static weight-lose test and electrochemical test with a self-made test device and its corrosion mechanism was analyzed. The results showed that the corrosion rate of 907A low alloy steel in simulated deep sea environment decreased gradually with the extension of immersion time, and finally tended to be stable. The dense and uniform rust layer effectively restrained the penetration of corrosive ions into the matrix and played a protective role. The main corrosion products were α-FeOOH, γ-FeOOH and Fe₃O₄. When the immersion time was prolonged, the conversion from γ-FeOOH to α-FeOOH reduced the corrosion rate of 907A steel. At the initial stage of immersion, pitting mainly occurred on the surface of 907A steel, which originated at the interface between matrix and inclusions. With the extension of immersion time, pitting gradually changed into uniform corrosion.