Cerium Coatings as an Alternative for Corrosion Protection of AZ91D Mg Alloy for Biomedical Applications

Abstract

This chapter is a compilation of investigations related to the formation of cerium coatings onto AZ91D Mg alloy in order to improve its corrosion resistance in simulated body fluid. The films were electrogenerated from solutions containing Ce(NO3)3 and other different components. The anticorrosive properties were analyzed by Electrochemical Impedance Spectroscopy (EIS) in Ringer solution at 37°C. The surfaces morphology of the films after the exposure to the corrosive environment were examined by SEM micrographs. For all cases the obtained morphology was typically mud-cracked. It was found that after 5 h of immersion in Ringer solution the films remain almost unaltered. Cerium based films have demonstrated to be a promising option to enhance the corrosion resistance of the Mg based alloy. The protective characteristics of the coatings could be attributed not only to the physycal barrier properties but also to the formation of insoluble chelates onto the substrate surface. Moreover, under determinated conditions, cerium films have self-healing properties. The films were mainly composed by cerium oxides and hydroxides and magnesium hydroxides.