Abstract
Ti-based materials are widely used for dental and orthopaedic implant applications due to their adequate mechanical properties, corrosion behaviour and biocompatibility. However, these materials are biologically inert and display poor wear resistance. In one of the most studied processes that aims to overcome these drawbacks, Ti surfaces are often covered by anodic oxide films with the incorporation of bioactive agents such as Ca and P. Although there are several works on the tribocorrosion behaviour of MAO-treated Ti surfaces, the influence of electrolyte composition on the corrosion kinetics under sliding is yet to be fully understood. In the present work, anodic oxide films were produced on cp-Ti surfaces with different calcium acetate concentrations in the electrolyte. Tribocorrosion behaviour was investigated by reciprocating sliding tests performed in 8 g/L NaCl solution at body temperature, under potentiostatic conditions. The results showed that higher concentrations of calcium acetate had a detrimental effect on tribocorrosion kinetics, however, they resulted in less mechanical damage due to alterations in the topography and structure of the MAO layer.
Highlights
Ti and Ti alloys are widely used in dental and orthopaedic implants due to their adequate mechanical properties, high corrosion resistance and biocompatibility [1,2]
The results showed that the overall tribocorrosion resistance can effectively be controlled by optimizing the surface chemistry, together with the rutile to anatase ratio by selecting the correct micro-arc oxidation (MAO) treatment parameters
By increasing the calcium acetate concentration, the conductivity of the electrolyte increases; this is the main reason for the enlargement of pore size [16,25,26,27]
Summary
Ti and Ti alloys are widely used in dental and orthopaedic implants due to their adequate mechanical properties, high corrosion resistance and biocompatibility [1,2]. Low tribocorrosion resistance is a considerable drawback once these implants are subjected to the cyclical mechanical solicitations present in a corrosive environment such as the human body [3]. Among the techniques that can be used, micro-arc oxidation (MAO) or plasma electrolytic oxidation (PEO) is one of the most well-known. In this process, several hundreds of volts are applied to a Ti substrate (immersed in an electrolyte) to promote the dielectric breakdown of a native passive film, and micro-arc discharges, which result in the formation of a thick and micro-porous oxide layer [8,9,10,11]. By controlling the process parameters, mainly electrolyte composition, applied voltage or current, and treatment time, it is possible to tailor the MAO layers in terms of thickness, topography, and chemical composition [12]
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