Investigation of the Electrochemical Activity of mixed metal oxide coatings of IrO۲, RuO۲, TiO۲ and Ta۲O۵ as Anode in the Cathodic Protection Systems by Impressed Current

Ternary coatings of RuO۲-TiO۲-IrO۲ and RuO۲-TiO۲-Ta۲O۵ were synthesized in two steps; first by sol-gel procedure and then thermal decomposition at ۴۵۰oC on Ti substrate. Electrocatalytic activity of the coatings toward oxygen evolution reaction was investigated by electrochemical methodes including cyclic voltammertry, electrochemical impedance spectroscopy in a ۱mol.L-۱ Na۲SO۴ solution in order to evaluation of their application as anode in cathodic protection systems. Electrochemically determined active surface area values revealed ۱.۹۷cm۲ active surface for the coating containing IrO۲ and ۰.۷۱cm۲ for the coating containing Ta۲O۵. In the case of the coating containing Ta۲O۵, addition of Ta۲O۵ has led to decreasing the active sites of RuO۲ as the main electrocatalyst for oxygen evolution. Morphological analysis of the coatings was conducted by providing the scanning electron microscope images and energy dispersive x-ray spectrums of coatings. The images clearly confirmed that IrO۲ aggregates at the cracks and spaces between the island like structures of ternary coating of RuO۲-TiO۲-IrO۲ and creates extra active sites. Enhancement of uniformity as a result of occupation of cracks improves the stability of the coating containing IrO۲.