Formation of Al-Si Composite Oxide Films on Aluminum by Electrophoretic Sol-Gel Coating / Anodizing

摘要

Highly pure aluminum specimens (99.99 %) with electropolishing or DC-etching were covered with SiO_2 films by electrophoretic sol-gel coating, and were anodized in a neutral borate solution. Structure and dielectric properties of the anodic oxide films were examined by SEM, TEM, EDX, and electrochemical impedance spectroscopy. It was found that anodizing of both specimens after electrophoretic deposition lead to the formation of anodic oxide films consisting of an inner alumina layer and an outer Al-Si composite oxide layer. The anodic oxide films formed thus had slightly higher capacitances than anodic oxide films on aluminum without any coating. Higher heating temperatures after electrophoretic deposition caused the capacitance of anodic oxide films to increase.