Effect of the addition of calcium salts on the structure and anticorrosion properties of siloxane-poly(hydroxyethyl methacrylate) hybrid coating applied on Ti-6Al-4V alloy

Abstract

Siloxane-pHEMA hybrid coatings with the addition of calcium chloride and calcium sulfate during the synthesis of the material were produced by the sol–gel method and deposited on Ti-6Al-4V alloy by dip-coating. The structural characteristics of the hybrid materials were analyzed by means of Nuclear Magnetic Resonance and Small/Wide Angle X-ray Scattering; their morphological properties were analyzed by means of Scanning Electron Microscopy and Atomic Force Microscopy. The electrochemical behavior and resistance to corrosion of hybrid coatings with and without addition of calcium salts were analyzed by means of Electrochemical Impedance Spectroscopy. The results showed that the coatings were homogeneous due to the rigid silica network formed during the polymerization, hydrolysis and reactions of condensation. In the sample, into which calcium sulfate was added, there was a decrease of the average roughness value (15.0 nm), while exhibiting regular topography and good adhesion to the substrate, suggesting that this coating has appealing characteristics for anticorrosive applications. Electrochemical tests in simulated body fluid (that underwent simulation) showed that the coatings with hybrid system showed better properties of a barrier with up to 96 h of immersion, in comparison to samples without coating. Therefore, these coatings showed promising features suitable for anticorrosion applications in biomaterials. Moreover, due to the addition of calcium sulfate, coatings made it possible to convey a good balance between biological and anticorrosion properties and, which in itself allows biocompatibility without compromising resistance to corrosion.