Development of biocompatible and corrosion-resistant plasma electrolytic oxidation coating over zinc for orthopedic implant applications

Abstract

The potential use of zinc in biomaterials is immense and lies unexplored to a greater extent. The recent research on zinc indicates the possibility of utilising zinc as a biodegradable biomaterial. Zinc-based materials with reduced corrosion rates in biological media may enable them as temporary orthopedic implant applications. This work aims to develop a biocompatible and corrosion-resistant plasma electrolytic oxidation (PEO) based coating over zinc. Different PEO coatings were fabricated on zinc in electrolyte systems consisting of various percentages of sodium meta silicate and borax decahydrate (75:25, 50:50, and 25:75) and a fixed amount of potassium hydroxide. After the successful fabrication of the PEO coating over the zinc, its morphological features, coating adhesion strength, wettability, corrosion resistance, and, most importantly, cytotoxicity is examined. The coating was peeled off on sample PEO treated with silicate to the borax decahydrate ratio of 75:25. In contrast, higher coating thickness, good corrosion and scratch resistance without any peeling were observed for the samples with silicate to borax decahydrate ratios of 50:50 and 25:75. Meanwhile, the cytotoxicity tests showed that the sample coated in the electrolyte comprised of an equal proportion of silicate and borax decahydrate (50:50) is better than the one coated in silicate: borax decahydrate ratio of 25:75, due to its favourable chemical composition, roughness, and wettability. Considering the physicochemical properties and biocompatibility, it can be concluded that the Zn PEO treated with silicate and borax decahydrate (50:50) is the appropriate candidate material for orthopedic applications.