Corrosion Behavior of A588 Weathering Steel in Simulated Seawater Environments with High Salinity and Low pH

A588 weathering steel is a commonly used material in marine structures due to its high corrosion resistance. However, in highly saline and low pH seawater environments, its corrosion resistance may be compromised. This study aims to investigate the corrosion behavior of A588 weathering steel in simulated seawater environments with high salinity and low pH.

Experimental Setup

A588 weathering steel specimens were prepared and exposed to synthetic seawater solutions with different salinity levels and pH values. The salinity levels of the solutions were 35, 50, and 70 ppt, while the pH values were 5, 6, and 7. The specimens were exposed for up to 30 days, and their corrosion rates were measured using weight loss analysis, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization tests.

Results and Discussion

The weight loss analysis showed that the corrosion rate of A588 weathering steel increased with increasing salinity and decreasing pH of the seawater solutions. At a salinity level of 35 ppt and pH of 7, the corrosion rate was 0.027 mm/yr. At a salinity level of 70 ppt and pH of 5, the corrosion rate increased to 0.618 mm/yr.

The EIS results showed that the seawater solutions with high salinity and low pH promoted the formation of a thick and porous rust layer on the surface of the specimens. This layer acted as a barrier and hindered the diffusion of oxygen and metal ions to the steel surface, thereby reducing the rate of corrosion.

The potentiodynamic polarization tests showed that the corrosion potential of A588 weathering steel shifted towards more negative values with increasing salinity and decreasing pH of the seawater solutions. This indicates that the steel became more susceptible to corrosion in these conditions.

Conclusion

In simulated seawater environments with high salinity and low pH, the corrosion rate of A588 weathering steel increased as the salinity level increased and the pH decreased. The formation of a thick and porous rust layer on the surface of the specimens reduced the rate of corrosion. However, the corrosion potential of the steel shifted towards more negative values, indicating that the steel became more susceptible to corrosion. These findings suggest that the use of A588 weathering steel in marine structures should be carefully considered, and appropriate measures should be taken to minimize the exposure to highly saline and low pH seawater environments.