Study of the growth mechanism of some oxide scales on alloy 230 in High Temperature Vapor Electrolysis (HTVE) conditions

摘要

Alloy 230 (also named Haynes 230) was tested as interconnect for production of hydrogen via High Temperature Vapor Electrolysis (HTVE). Samples were oxidized at 800°C in the both atmospheres representative of the HTVE operating conditions: Ar-1%H_2-9%H_2O (for cathode side) and air (for anode side). The high temperature oxidation behaviour was studied in both atmospheres together with the electrical conductivity of the thermally grown oxide scales. Oxidation kinetics indicated lower oxidation rate in H_2/H_2O compared to air (k_p = 3.8·10~(-15)g~2·cm~(-4)·s~(-1) in H_2/H_2O and k_p = 1.6·10~(-14)g~2·cm~(-4)·s~(-1) in air). The corrosion products were characterized by scanning electron microscopy associated with X-ray diffraction analyses and energy dispersive X-ray analyses. The sample electrical behaviour was evaluated by determining the Area Specific Resistance (ASR). The ASR was higher in H_2/H_2O (ASR = 1 ohm.cm~2) than in air (ASR = 0.04 ohm·cm~2). The diffusion of proton or hydrogen containing species through the oxide scale is proposed to be responsible for the increase of the electrical conductivity in cathode side.