過塩素酸水溶液中におけるAl-Ga合金電極のアノード溶解挙動

Abstract

In order to obtain fundamental information on the corrosion characteristics of Al-Ga alloy, anodic dissolution behavior of Al-Ga solid solution alloy in a dilute HClO4 solution was investigated by the measurements of the anodic polarization curves of Al, Ga and Al-Ga alloy electrodes, the X-ray diffraction analysis of the corrosion products on the electrode surface and the SEM observation of the electrode surface after the corrosion test.The main experimental results obtained are summarized as follows:(1) The corrosion potentials of Al-Ga alloy electrode in a dilute HClO4 solution depend on both the content of Ga in the alloy and the solution temperature. The corrosion potentials decrease with an increase in the Ga content and the solution temperature, and the corrosion resistance of the alloy is decreased. However, the corrosion potentials of the alloy are almost constant at the Ga contents more than 5 mass%.(2) The dependence of the corrosion behavior of Al-Ga alloy electrodes on the solution temperature changes at about 298 K. The corrosion rate is inhibited by the formation of hydroxides such as Al(OH)3, Ga(OH)3 and β-Ga2O3 at the temperature lower than 298 K. However, the corrosion rates increase with an increase in the temperature above 298 K.(3) The corrosion of Al-Ga alloy proceeds by selective dissolution of Al component from the grain boundary layer of the alloy.(4) The corrosion rates of Al-Ga alloy decrease in the order Al-4.7 mass%Ga alloy≥Al-15.8 mass%Ga alloy>Al-0.675 mass%Ga alloy>pure Al>pure Ga.