Electrophoretic deposition of chitosan/bioactive glass/silica coatings on stainless steel and WE43 Mg alloy substrates

Two electrophoretic coatings consisting of chitosan/bioactive glass/silica on magnesium alloy (WE43) and on stainless steel (316L) substrates are described. The partial replacement of bioactive glass with silica particles gives a topography favorable for the formation of hydroxyapatite, when the coatings are in contact with simulated body fluid (SBF). Both coatings are compared in terms of composition (thermogravimetric analysis), corrosion resistance (electrochemical impedance spectroscopy and electrochemical polarization curves), scratch resistance (instrumented micro-indentation and scratch test) and bioactivity (immersion in simulated body fluid). Although the addition of silica decreases the adhesion of the coating to the steel substrate, it has no influence on the coating adhesion on the Mg alloy. The results show the advantageous effect of adding silica particles (increasing coating bioactivity and hardness) while keeping the organic (chitosan) concentration constant.