Corrosion of Candidate Materials for Use in Alkaline Water Electrolysis

Abstract In alkaline water electrolysis the capital expense (CAPEX) of the electrolyzer unit is high and cost reduction, wherever possible, is highly desired. Many parts are made of expensive nickel-based alloys, which in some cases may be an overly conservative option. Careful evaluation of the operating conditions may reveal that expensive alloys may be replaced by cheaper ones in parts of the system. In this paper the corrosion behavior of candidate materials, relevant for use in atmospheric and pressurized alkaline water electrolysis systems, is evaluated at typical operating conditions (i.e. 1-30 bar pressure, 60-80°C and 25 wt% KOH). The materials tested are one austenitic stainless steel (UNS S31603), one super duplex stainless steel (UNS S327X0) and one carbon steel (UNS K03014), with one nickel base alloy (UNS N06625) included in the matrix as a reference material. Performance is evaluated based on mass loss corrosion and localized corrosion based on surface profilometry. Corrosion scales and their protectiveness are evaluated based on analysis using SEM/EDS and XRD. Carbon steel was found to have lower corrosion rates than the other steels at all temperatures.