Investigation of the Electrochemical Activity of mixed metal oxide coatings of IrO2, RuO2, TiO2 and Ta2O5 as Anode in the Cathodic Protection Systems by Impressed Current

Ternary coatings of RuO2-TiO2-IrO2 and RuO2-TiO2-Ta2O5 were synthesized in two steps; first by sol-gel procedure and then thermal decomposition at 450oC 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 1mol.L-1 Na2SO4 solution in order to evaluation of their application as anode in cathodic protection systems. Electrochemically determined active surface area values revealed 1.97cm2 active surface for the coating containing IrO2 and 0.71cm2 for the coating containing Ta2O5. In the case of the coating containing Ta2O5, addition of Ta2O5 has led to decreasing the active sites of RuO2 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 IrO2 aggregates at the cracks and spaces between the island like structures of ternary coating of RuO2-TiO2-IrO2 and creates extra active sites. Enhancement of uniformity as a result of occupation of cracks improves the stability of the coating containing IrO2.