Influence of stoichiometry on the corrosion response of titanium oxide coatings produced by plasma electrolytic oxidation

In this study the corrosion mechanism leading to coating debonding in acidic environments, produced by plasma electrolytic oxidation (PEO) on Ti, is investigated through electrochemical impedance spectroscopy (EIS), potential step chronometric, and a detailed structural characterization according to the use of electron energy loss spectroscopy (EELS). It will be demonstrated that a slightly reduced oxide will enhance proton adsorption and percolation leading to oxide debonding, while the synthesis of a barrier layer mainly composed by Ti 4 + oxide bearing phases and low sulfur content will retard H + permeation enhancing H2 evolution in correspondence of the oxide surface.