Electrochemical corrosion behavior of high strength steel in simulated deep-sea environment under different hydrostatic pressure

Abstract

The corrosion behavior of Ni-Cr-Mo-V high strength steel in the simulated deep-sea environment under different hydrostatic pressure and immersion time is investigated using electrochemical techniques, microscopic morphology observation and Raman spectrometer. During the first 10 days immersion, the corrosion rate presents wave-like changes. The corrosion rate under different hydrostatic pressure tends to be stable after 10 days immersion. The area with uneven composition will preferentially dissolve and form corrosion pits. The local corrosion takes the corrosion pit as the center, expands and fuses around, and finally forms uniform corrosion. High hydrostatic pressure promotes β-FeOOH transforming into other corrosion products. The anode of the steel tends to active dissolution and the cathode show oxygen diffusion control characteristics at the initial stage of corrosion. Under 20 MPa, step-shape passivation appears in the anode region. Due to the rapid reaction, the corrosion product film has poor protection performance and dissolves, which resulting in not obvious passivation phenomenon.

Keywords

• High strength steel
• Deep-sea corrosion
• Microstructure morphology
• Electrochemical characteristics
• Corrosion products