Surface properties and corrosion protection study of a poly(N-ethyl-4-vinylpyridine) polyelectrolyte-based coating on an electrochemically formed Ti|TiO2 surface

In this study, the surface properties and corrosion behavior of a titanium sample modified with an electrochemically formed oxide layer (Ti|TiO2) and Ti|TiO2 sample coated with poly(N-ethyl-4-vinylpyridinium) cations (PE4VP) were studied. It was shown, by means of atomic force microscopy and ellipsometry, that the Ti|TiO2 surface is very flat with an average roughness of only 3.4 nm and an oxide layer thickness of 16.1 nm. The inner surface potential of the Ti|TiO2 sample as a function of pH and concentration of sodium chloride was measured using the constructed Ti|TiO2 electrode. In order to improve the corrosion protective effectiveness of the surface coating, the process parameter conditions for strong poly(N-ethyl-4-vinylpyridinium) cation optimal adsorption on the electrochemically formed TiO2 oxide layer were determined using ellipsometry, tensiometry, and atomic force microscopy. The effect of adsorption of PE4VP cations on the inner surface potential and corrosion protection effectiveness of the TiO2 and TiO2-PE4VP coatings was examined. The electrochemical behaviour and corrosion properties of an unmodified titanium surface, titanium surface modified with an electrochemically formed TiO2 and subsequently modified with a PE4VP polyelectrolyte-based coating were examined by means of electrochemical impedance spectroscopy. Increased polarization resistance values and high corrosion protection effectiveness after surface modification with the PE4VP coating indicate the formation of a highly protective coating with high corrosion resistance imparted to the underlying titanium. The results presented here provide an insight into the optimization of strong polyelectrolyte cation adsorption process parameters and demonstrate that application of a PE4VP coating is a suitable method for surface modification of titanium to enhance corrosion protection in an aggressive environment.