A novel approach to the role of iridium and titanium oxide in deactivation mechanisms of a Ti/(36 RuO2-x IrO2-(64-x) TiO2) coating in sodium chloride solution

Iridium and Titanium oxide are known as the corrosion-resistant and bonding agents for mixed metal oxide coatings. Based on this fact, this study aims to investigate the effect of these oxides on the deactivation mechanisms of a typical Ti/(36RuO2-xIrO2-(64-x)TiO2) in sodium chloride solution. The coating with quantities of 16, 26, and 36 wt. % titanium oxide is applied by thermal decomposition method. Then, a comprehensive analysis is carried out on the coating's morphology and microstructure by electron microscopy, energy dispersive spectroscopy, and grazing incidence X-Ray diffraction analysis. Additionally, cyclic voltammetry, accelerated lifetime test, and electrochemical impedance spectroscopy is performed to investigate the coating's electrochemical properties and corrosion behavior. The results show that the anode with the coating of nominal composition Ti/(36RuO2-38IrO2-26TiO2) provides a nanostructured morphology, solid solutions of (Ru, Ir)O2 and (Ru, Ir, Ti)O2, with maximum lifetime and optimum electrocatalytic activity. This composition results in an improved bonding of the coating components, which delays pitting corrosion of the coating in sodium chloride solution. Ultimately, the predominant corrosion and deactivation mechanism is changed into the general dissolution of the electrocatalytic component which has enhanced durability of the coating.