The role of the concentration profile of titanium oxide on the electrochemical behavior of RuO2-TiO2 coatings obtained by the sol-gel procedure

Abstract

In order to understand the role of TiO2 in the deactivation mechanism of an active RuO2–TiO2 coating, an additional TiO2 layer was introduced in the support coating interphase of regular Ti//[RuO2–TiO2 anode in one case and on the surface of the coating in the other. The electrochemical behavior of these, with TiO2 enriched, anodes was compared with the behavior of anodes with regular RuO2–TiO2 coatings, which were subjected to an accelerated stability test. A high-frequency semicircle in the complex plane plot obtained by electrochemical impedance spectroscopy, for a regular RuO2–TiO2 coating corresponds to TiO2 enrichment in the coating as a consequence of anode corrosion. In the case of the coatings with additional TiO2 layers, a high-frequency semicircle was not observed. The additional TiO2 layers increase the coating overall resistance and influence the coating impedance behavior at low frequencies. Similar equivalent electrical circuits were used to analyze the impedance behavior of coatings having an additional TiO2 layer at different position within RuO2–TiO2 coating.

U cilju ispitivanja uloge titan-oksida u deaktivaciji RuO2–TiO2 prevlake na titanskoj podlozi, ispitivane su osobine anoda sa dodatnim slojem TiO2 u međufazi podloga prevlaka, odnosno na površini prevlake. Elektrohemijsko ponašanje ovih upoređeno je sa ponašanjem anoda sa uobičajenom RuO2–TiO2 prevlakom, kao i sa onima koje su bile podvrgnute ubrzanom testu stabilnosti. Pojava polukruga u visoko-frekventnoj oblasti u dijagramima u kompleksnoj ravni, koja je registrovana spektroskopijom elektrohemijske impedancije za uobičajene RuO2–TiO2 prevlake, a koja je posledica obogaćivanja prevlake sa TiO2 tokom njene deaktivacije, nije uočena kod anoda sa dodatim TiO2 slojem. Dodati TiO2 slojevi povećavaju omsku otpornost prevlake i utiču na impedancijsko ponašanje pri niskim frekvencijama. Za analizu impedancijskog ponašanja prevlaka sa dodatim TiO2 slojevima kao i uobičajenih RuO2–TiO2 prevlaka koje su deaktivirane korišćena su slična ekvivalentna električna kola.