Crevice Corrosion of Q235 Steel in Simulated Seawater

The crevice corrosion of Q235 steel in simulated seawater was studied using a wire beam electrode (WBE) in combination with electrochemical impedance spectroscopy (EIS). In addition, iron selective electrodes (ISE) were used as a senser to monitor the concentration change of H⁺ and Cl^- in different stages of crevice corrosion. The results indicated that the propagation of the crevice corrosion complied with the theory of oxygen concentration cell followed by occluded corrosion cell. The concentration of H⁺ and Cl^- kept increasing in the initiation and enlargement periods of the crevice corrosion, and the extreme values of the composition of the solution were pH 2.43 and Cl^- concentration of 3.45 mol·L^-1 within the crevice. The corrosion progress complies with Bockris mechanism after the occluded cell began to take control with a good linear correlation between pH and the concentration of Cl^-. The crevice corrosion probability of Q235 steel was statistically estimated to be 73.3%, and the pitting ratio was 6.1%.