PMMA-SiO2 Organic-Inorganic Hybrid Coating Application to Ti-6Al-4V Alloy Prepared through the Sol-Gel Method

Abstract

Siloxane-poly(methyl methacrylate) (PMMA) hybrid was synthesized based on the sol-gel method and applied to Ti-6Al-4V through dip-coating. The structural feature of the hybrid was subjected to Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TG); its morphological properties were analyzed through scanning electron microscope (SEM), energy dispersive spectrometry (EDS), atomic force microscopy (AFM) and contact angle. The electrochemical behavior and corrosion resistance of both the hybrid coating and the uncoated substrate were investigated based on electrochemical impedance spectroscopy (EIS) and scanning vibrating electrode technique (SVET). Results showed homogeneous coating formation due to the rigid hybrid network formed during polymerization, hydrolysis and condensation reactions. This outcome suggested interaction between the organic (methyl methacrylate (MMA)) and inorganic (tetraethyl orthosilicate (TEOS)) phases, which was favored by the coupling agent (3-(trimethoxysilyl)propyl methacrylate (TMSM)). The S0M (PMMA-SiO 2 hybrid Ti-6Al-4V coated alloy) film presented regular topography and adherence to the substrate. Electrochemical simulated body fluid (SBF) tests showed that the hybrid coating presented better barrier properties (168 h of the immersion time) than the uncoated substrate, fact that makes it an interesting material for anti-corrosive applications in biomaterials.

Influence of simulated body fluid (normal and inflammatory) on corrosion resistance of anodized titanium

“…This finding is in accordance with the literature (Ammar et al, 2016;Prządka et al, 2016 ;J. Santana et al, 2020), which states that the surfaces of solids with greater roughness can promote local changes in surface energies, which results in contact angle values different from those measured at an equilibrium condition.…”

“…The OCP monitoring values (Figure 11) obtained for the barrier, porous samples were very close to the values of the cp grade 2 open circuit potential in the two electrolytes studied. This was already expected, as described in the literature, once the corrosion resistance of titanium is provided by the formation of a stable, adherent and protective passive oxide film which promotes certain stability against corrosive electrolytes (Santana et al, 2020); Salvador et al, 2017). In this way, among the most common oxides of titanium, the most stable is titanium dioxide, spontaneously formed on the metal surface, responsible for the protective characteristic against corrosive processes (Marino et al, 2001).…”

“…After 48 hours of immersion in healthy SBF, a high frequency phenomenon associated with the anodized layer is observed, which denotes resistance to charge transfer. A medium frequency phenomenon associated with the contribution of the native titanium oxide layer also can be observed (Santana et al, 2020). However, after 120 hours, the phenomenon decreases with the time of immersion due to the permeability of the electrolyte through the anodized layer.…”