Study of Conductivity of K41X Chromia Forming Alloy in High Temperature Electrolysis Environment

Abstract

Alloy K41X has been proposed as interconnect material for high temperature vapor electrolysis (HTVE) devices. This chromia forming alloy (alloy K41X) was oxidized at 800 °C in a thermobalance in oxidizing (synthetic air) and reducing (Ar–1 %H2–9 %H2O) environments for 250 h. The evolution of the contact resistance was evaluated using a dedicated device under the same conditions. There were higher oxidation kinetics rate in air than in Ar–1 %H2–9 %H2O but surprisingly, the corresponding area specific resistance (ASR) values were 20 times higher in Ar–1 %H2–9 %H2O mixture than in air. Additional tests and analyses (exposure in Ar–D2–H2O environment, GD-OES and SIMS analyses) clearly showed that the higher ASR value can be attributed to the presence of hydrogen in the oxide scale when exposed in Ar–H2–H2O mixture. In situ changes of atmosphere during ASR measurement showed the rapid kinetics for hydrogen desorption.