Driving forces in the corrosion dynamics of stainless steels in different aquatic environments

Corrosion is a critical factor in maintaining the integrity of marine facilities such as ship structures, offshore platforms, and other infrastructure, as it leads to surface deformation, including cracking and pitting. This research presents a comparative study of the effects of marine and other aquatic environments on AISI 304, AISI 304L, AISI 316L, and AISI 420 stainless steel (SS) metals. Tafel polarization tests were conducted to evaluate the breakdown potential of the passive film for these four SS types under different aquatic conditions. Corrosion resistance increased in the order AISI 420 < AISI 304 < AISI 304L < AISI 316L. The best-performing materials in all media were AISI 316L and AISI 304L, which exhibited the widest passive range, the lowest corrosion current density, and the highest polarization resistance. The results reveal that the breakdown potential is lower at higher salinity, indicating that increasing the ionic species and salt concentrations in seawater also increases corrosion attack on the metal surface. Based on the study’s outcomes, corrosion rates after 30 days ranged from 0.050 mm y⁻¹ to 0.0245 mm y⁻¹. The I_corr value of AISI 304L steel decreased significantly from 72.43 to 6.11 μA cm⁻² after 30 days of exposure, While AISI 420 SS and AISI 304 were the most affected by corrosion in seawater.