Abstract
In this study, the surface properties of Ti/TiO2 substrate before and after the adsorption of polyelectrolytes were investigated. As model polyelectrolytes, strongly charged polycation poly(diallyldimethylammonium) (PDADMA) and strongly charged polyanion poly(4-styrenesulfonate) (PSS) were used. Initially, the bare titanium substrate was characterized by means of ellipsometry, atomic force microscopy (AFM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and measurements of inner surface potential using crystal electrode (CrE). It was shown that the substrate surface is very smooth with the roughness of 3.5 nm and oxide layer thickness of 3.8 nm. After the adsorption of PDADMA and PSS, polyelectrolyte-coated titanium surface was examined using the above-mentioned methods under the same conditions. It was found that both PDADMA cations and PSS anions form a stable polymeric nanofilm on Ti/TiO2 surface that partially covers the surface, without significant impact on the surface roughness. The corrosion protection effectiveness values indicate that the corrosion properties were greatly enhanced upon polyion adsorption and polyelectrolyte coating formation on the flat TiO2 surface. The obtained results were additionally confirmed by inner surface potential measurements. According to the methods employed, PDADMA nanofilm modification offers enhanced corrosion protection to the underlying titanium material in sodium chloride electrolyte solution.
Highlights
Titanium and its alloys are widely employed materials
Many titanium properties are attributed to the passive oxide layer which spontaneously forms on the titanium surface in an oxygen-containing environment
In order to assess polyelectrolyte coating’s stability and level of corrosion protection, cyclic voltammetry measurements for prepared Ti substrates were performed in the wide potential range with anodic limit shift, Eal from 1.0 V to 3.0 V at the scan rate, ν = 100 mV s−1
Summary
Titanium and its alloys are widely employed materials. Many titanium properties are attributed to the passive oxide layer which spontaneously forms on the titanium surface in an oxygen-containing environment. The several independent experimental methods, ellipsometry, atomic force microscopy (AFM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and measurements of surface potential by means of crystal electrode (CrE), were applied to study the film thickness and surface morphology, electrical surface properties as well as anticorrosive effects. Such systematic studies are needed to elucidate in what extent polyelectrolyte coatings on flat metal oxide surfaces influence various surface properties. Oxide and polyelectrolyte thicknesses were determined at ten different positions on each sample and are presented as the average (with the standard error) of measurements for two individual samples
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