Evaluation of the Electrochemical Activity and Stability of Ti/IrO2–Ta2O5 Electrode as Anode in the Cathodic Protection Systems via Impressed Current

Abstract

Ti/IrO₂–Ta₂O₅ electrode with 70% IrO₂ (in mole ratio) was synthesized by thermal decomposition of iridium and tantalum chloride salts at 450°C. Stability of the electrode as dimensionally stable anode in impressed current cathodic protection systems was investigated in a mixture of 1 mol L^–1 sodium sulfate and 1 mol L^–1 sulfuric acid at 30°C under 1.5 A cm^–2 constant current density. For this purpose, the potential of work electrode (anode) was recorded against time during the stability test. The changes in electrochemical properties of the electrode were fallowed using electrochemical impedance spectroscopy and cyclic voltammetry at different times of stability test. In addition, Tafel polarization test was done at the beginning of stability test in order to studying the mechanism of oxygen evolution reaction at the surface of the electrode. Morphological analysis was done by means of field emission scanning electron microscope and Energy-dispersive X-ray spectrometer. The results indicated that the durability of the electrode at concentrated acidic sulfate medium is about 88 hours and the oxygen evolution reaction proceeds through the redox exchanging of different iridium oxide species.