In-vitro degradation behavior of hybrid epoxy-alkyl sol–gel/anodized composite coating on AZ31B Mg alloy

Abstract

AbstractMg alloys are considered a promising alternative to use as biodegradable implants. However, the main limitations of these alloys are the high susceptibility to hydrogen evolution and corrosion. Consequently, it is necessary to control the corrosion rate through surface treatment techniques. In this regard, a double layer system, based on the first deposition of a MgO coating and the subsequent deposition of an organo-silane sol-gel coating (anodized/SGMI) was proposed to increase the biocompatibility and reduce the corrosion rate of Mg alloy. Sol-gel coatings were prepared using methyltriethoxysilane (MTES), (glycidyloxypropyl) trimethoxysilane (GPTMS), SiO2 nanoparticles, and 1-methyl imidazole (1-MI). 29Si and 13C NMR measurements were performed to investigate the inorganic-organic network formation during the sol-gel synthesis, and to characterize the structure of the cured silane coating. According to the results, the addition of 1-MI mainly promotes the condensation reaction of GPTMS and MTES. After sol-gel deposition, a higher cross-linking coating network was obtained and the degradation of AZ31B Mg alloy in simulated body fluid (SBF) was slowed down. The control of the hydrogen and pH evolution over 450 h suggest that the anodized/SGMI coating system may be suitable for short-term implants applications; particularly for applications that are expected to degrade after 10-12 days such as surgical skin staples. Graphical Abstract