Increasing corrosion resistance of a ZrTi alloy with a bioinspired coating with low porosity

Abstract

The paper is focused on elaboration and characterization of bioinspired coatings on ZrTi with different porosities as a result of various components ratio of hydroxyapatite (Hap) and chitosan (CS). Three different ratios of HAp:CS were used for coating the specimens. The coatings surface was analyzed using scanning electron microscopy (SEM) and by measuring the contact angles. All samples have a hydrophilic character, which is more significant for lowest chitosan content. The corrosion resistance was investigated in Afnor artificial saliva using Tafel procedure and EIS technique. Corrosion current variations can be attributed to defects present in the coating. Pores present in the coating connected the electrolyte to the substrate surface and the results an acceleration of corrosion. A stability scale was established according to corrosion rate of samples and their porosity, indicating as most resistant to corrosion the sample with lowest porosity. The impedance data and the equivalent circuits presented were obtained for both the uncoated and coated samples immersed at initial time and at time higher than 24 h. EIS data permitted a discussion of diffusion process as well.