Anticorrosion and Cytocompatibility Assessment of Graphene-Doped Hybrid Silica and Plasma Electrolytic Oxidation Coatings for Biomedical Applications

Abstract

Magnesium AZ31 alloy substrates were coated with different coatings, including sol–gel silica-reinforced with graphene nanoplatelets, sol–gel silica, plasma electrolytic oxidation (PEO), and combinations of them, to improve cytocompatibility and control the corrosion rate. Electrochemical corrosion tests, as well as hydrogen evolution tests, were carried out using Hanks’ solution as the electrolyte to assess the anticorrosion behavior of the different coating systems in a simulated body fluid. Preliminary cytocompatibility assessment of the different coating systems was carried out by measuring the metabolic activity, deoxyribonucleic acid quantification, and the cell growth of premyoblastic C2C12-GFP cell cultures on the surface of the different coating systems. Anticorrosion behavior and cytocompatibility were improved with the application of the different coating systems. The use of combined PEO + SG and PEO + SG/GNP coatings significantly decreased the degradation of the specimens. The monolayer sol–gel coatings, with and without GNPs, presented the best cytocompatibility improvement.

Plasma Electrolytic Oxidation of Az31 Magnesium Stents for Degradation Rate Control

“…The products generated during the hydrolysis are then re-deposited and accumulated inside the pores of the PEO coating thus sealing them and increasing the dielectric behavior provided by the coating. Also, the build-up of undercoating corrosion products provides an additional protection, which will be further discussed later on when revealing the Published data related to PEO coatings on magnesium substrates claim much higher polarization resistance than the values obtained in the present study [21]. However, it must be noticed that one of the goals of this research is to create thin layers of a few microns in order to control the degradation rate of the stents once implanted in arteries, and not to completely avoid the degradation of the implants.…”

“…For applying of the PEO coating, the samples were immersed in an electrolyte which composition, shown in Table 1, was developed in previous research [21].…”

Advances in the Modification of Silane-Based Sol-Gel Coating to Improve the Corrosion Resistance of Magnesium Alloys

“…This treatment converts the surface of the metal into a thin film of metal oxides/other compounds that are chemically bonded to the surface [ 3 , 11 , 102 ]. However, most chemical conversion coatings or anodizing treatments (like plasma electrolytic oxidation (PEO) or micro-arc oxidation (MAO)) have cracks and pores, which cannot provide ideal corrosion protection effects, while sol-gel can provide functions such as sealing pores or providing biocompatibility [ 103 , 104 ]. This section mainly reviews the influence of the combination of chemical conversion coating, electrochemical oxidation coating and sol-gel on the anticorrosion effect of Mg alloys.…”

Graphene-based anti-corrosion coatings on magnesium alloys: a review

“…In addition, there has been a lot of research into sol-gel coatings as a post-treatment for sealing underlying coatings. Fernandez et al [113] sealed a PEO coating with a sol-gel method to lock a corrosion inhibitor into the pores of the PEO coating, substantially enhancing the corrosion resistance of the composite coating. However, micro-cracks easily form on the surface when the sol-gel method is used to prepare thick multilayer coatings, due to the large internal stresses, and the anti-corrosion performance cannot be optimal if the coating is too thin.…”