Design of TEOS-GPTMS sol-gel coatings on rare-earth magnesium alloys employed in the manufacture of orthopaedic implants

Abstract

In the present work hybrid sol-gel coatings were synthesized on different magnesium alloys with potential interest in the fabrication of orthopaedic implants. Hybrid sols were obtained from a mixture of the inorganic precursor tetraethoxysilane (TEOS) and the organic precursor 3-glycidoxypropyltrimethoxysilane (GPTMS), employing ethanol as solvent and acetic acid as catalyst. The characterization of the sols was performed using pH measurements, rheological tests and infrared spectroscopy (FTIR) for different aging times. On the other hand, the coatings were characterized by scanning electron microscopy (SEM), while the corrosion resistance was evaluated using anodic polarization in SBF solution at 37±2°C. The results confirmed that, under specific conditions, uniform and homogeneous sol-gel coatings were obtained, which enhanced the corrosion resistance so that the corrosion current density was reduced in about two orders of magnitude with regard to the parent alloy.