Mott–Schottky analysis of aluminium oxide formed in the presence of different mediators on the surface of aluminium alloy 2024-T3

Corrosion protection of aluminium (Al) alloys is an important industrial problem. In the past it was solved with hexavalent chromium (Cr6+) coatings. However, these coatings are hazardous, and have to be replaced. One of the most promising alternatives to Cr6+ corrosion protection technology is the protection with intrinsically conducting polymers (ICPs). In order to advance this type of protection, this is necessary to understand properties of Al oxide formed in the presence of the electron transfer mediators, compounds that allow ICPs deposition on Al alloy surface. Due to low thicknesses of oxide layers on Al (of the order of a few nanometers) only a limited number of methods can be used to study its properties. In this paper we report the research of the properties of Al oxide by Mott–Schottky analysis, electrochemical technique that allows determining a variety of oxide parameters treating it as a semiconductor, ultra-thin layer with non-stoichiometric defects or substitutions. Electrochemically determined flat band potential and concentration of charge carriers in the oxide are discussed in correlation with the structure of electron transfer mediator that was applied during the oxide formation.