Green hydrogen is emerging as a leading alternative to fossil fuels for sustainable energy sources. Alkaline water electrolysis remains one of the most commercially robust and cost-effective technologies for production of green hydrogen. However, alkaline electrolysis operates in a highly aggressive environment with 30-40% KOH being used as electrolyte at 85-90oC temperature and 15 bars pressure. While the main components of alkaline electrolyzers such as electrodes are typically made of nickel-based alloys or nickel-coated substrates that demonstrate exceptional stability under these conditions, accessory materials such as pumps, heat exchangers, tubing, and joints are often made from stainless steel (e.g., 316L). Under harsh 30% KOH conditions, otherwise high corrosion resistant 316L shows pitting and intergranular corrosion. The corrosion of these accessory materials is a critical challenge affecting efficiency, durability, and safety of hydrogen production systems. Despite its widespread industrial use, the corrosion behavior and underlying degradation mechanisms of 316L under such extreme alkaline environments are still not well understood. Additionally, modern electrolyzer systems are pushing towards higher temperatures for increased efficiency, hence materials should withstand higher temperatures and pressures. This study focuses on determining the corrosion behavior of 316L stainless steel under simulated alkaline electrolysis conditions at atmospheric pressures. Investigations include simple immersion studies in 30% KOH (at temperatures 90°C, 95°C, and 100°C) for 7 days followed by Inductively Coupled Plasma (ICP) analysis of electrolyte and observation of surface morphology of corroded specimens. Electrochemical studies include Potentiodynamic Polarization experiments and LPR measurements. Scanning electron microscopy (SEM) revealed evidence of pitting corrosion and transition to intergranular corrosion (IGC) with increasing severity with temperatures, which is supported by electrochemical data. ICP analysis showed dissolution of Fe, Cr, and Mo, while Nickel was stable in the alkaline conditions, which was also supported by detailed XPS analysis. High resolution TEM analysis revealed segregation of slight amount of Cr at the grain boundary that was enough to cause IGC under harsh KOH conditions together with elevated temperature. Overall, the results showed significant difference in corrosion mechanisms for 316L under 30% KOH compared to other environments, which is important to understand.
