Corrosion of stainless steels and nickel-based alloys for alkaline water electrolysis

The corrosion behaviour of commercial austenitic stainless steels and nickel-based alloys in 38wt% KOH solutions was investigated between 120° and 180°C under hydrogen and oxygen overpressure. (a) In hydrogenated solutions, alloys containing 20% Ni or more are resistant to general corrosion and to stress corrosion cracking. (b) In oxygenated solutions, type AISI 304L SS are highly corroded and susceptible to SCC. Nickel-based alloys are resistant to SCC, but the general corrosion rate is high beyond a break-away point. Among these two types of materials, the most resistant alloys are found to be type 310(L) SS and Alloy 800. Taking into account SCC results, Alloy 800 is the best choice for water electrolysis within the temperature range 120°–150°C. The different materials tested are not resistant enough to corrosion at 180°C and even nickel is not satisfactory at this temperature.