Electrochemical Studies of Stainless Steel and Stainless Steel-TiO(2) Composite in Reference to Molten Aluminum Alloy Using a Solid-State BaCO(3) Electrolyte

The influence of TiO(2) addition on the high-temperature electrochemical characteristics of stainless-steel-based materials was investigated by means of differential potential measurement, electrochemical polarization and impedance spectroscopy. A new three-electrode approach was utilized which incorporated a liquid aluminum alloy AlSi7Mg0.3 as the reference electrode, barium carbonate BaCO(3) as the solid-state electrolyte, and stainless steel or a stainless steel-TiO(2) composite as the working electrode. The potential differences between the steel-based working electrodes and the liquid-aluminum-alloy reference electrode were measured for 85 h throughout the whole experiment, including the heating and cooling period. The experiments were performed at 850 °C. The determination of the high-temperature open circuit potential (E(Corr)) in reference to the liquid aluminum alloy was carried out via potentiodynamic polarization. The polarization-related changes in the impedance characteristics were evaluated by the correlation of impedance responses before and after the polarization. The addition of 40 vol% TiO(2) resulted in a reduction in the potential of the steel-TiO(2) composite and led to the formation of a more uniform electrode–electrolyte interface. The reaction products on the surface of the working electrodes were investigated by means of SEM/EDS and XRD. They consisted of mixed oxides within the Fe-O, Ba-Fe-O and Ba-Cr-O systems.