Estudo de corrosão de filme a base de hidroxiapatita produzidos por HVOF em solução de Hanks

Abstract

The electrochemical behavior of HVOF produced hydroxyapatite coatings was investigated using open circuit potential measurements, cyclic polarization (CP) curves and electrochemical impedance spectroscopy (EIS) in natural aerated Hank´s solution for 30 days. All samples presented some open circuit potential oscillations, which were associated to the porous nature of the coating that allows the electrolyte reaches the substrate causing pitting formation with activation – repassivation at the bottom of the pores. The polarization studies indicated that the HA-TiO2 coating (80-20 sample) was the only one that showed a clear passive region from around -0.4 V to 0 V in the presence and absence of BSA, indicating the beneficial influence of the addition of TiO2 to the HA coating stability. The impedance data were interpreted based on the presence of a metallic oxide layer between the HA or AH-TiO2 coating which are attacked and / or dissolved by the Hank´s solution with significant influence of the bovine serum albumin (BSA) when it is present in the electrolyte solution. Equivalent electrical circuits (EECs) with two or three time constants were used to fit the experimental data. Our results indicated that BSA in Hank´s solution diminishes the stability of the metallic oxide layer present on the Ti-based alloy and accelerates the hydroxyapatites dissolution due to its chelating ability.