Incorporation of ZrO2 particles in the oxide layer formed on Mg by anodizing: Influence of electrolyte concentration and current modes

Abstract

HypothesisThe objectives of the present study are to ascertain, particle incorporation during the initial stages of microarc oxidation (MAO), feasibility of increasing the level of particle incorporation through manipulation of process variables and, the use of MgO–ZrO2 composite coatings either as a pre-treatment or as a post-treatment for MAO coated Mg. ExperimentsAnodic oxide coatings were prepared using 0.3M NaOH+15g/l ZrO2 and 3M NaOH+15g/l ZrO2 at 10V under direct current, pulsed current (PC) unipolar and PC bipolar modes. MAO coatings were prepared using 5g/l NaOH+15g/l Na2SiO3 at 250V under direct current mode for 2min. FindingsThe study reveals that it is possible to incorporate ZrO2 particles in the anodic oxide layer, suggesting such a possibility during the initial stages of MAO. When the MgO–ZrO2 composite coating is used as a pre-treatment, it helps to reduce the size and density of the pores of the MAO coatings and increased the corrosion resistance. When it is used as a post-treatment, lamellar shaped Mg(OH)2 with a very high surface area is formed on the surface, which would be beneficial to impart a better bioactivity and to facilitate immobilization of biomolecules.