Determinación de la adhesión de hidroxiapatita sobre Ti cp utilizando impedancia electroquímica

Abstract

The electrochemical impedance spectroscopy is one of the most modern techniques used to characterize the electrical properties of a film and its adhesion to a metallic surface. This work represents part of a current project in which we propose to evaluate the solubility of a hydroxyapatite (HA) film, deposited on the polished surface of cp Ti by biomimetic method, after various periods of immersion in physiologic solution with the following composition (g/L): NaCl 8,74; NaHCO₃ 0,35; Na₂HPO₄ 0,06; NaH₂PO₄ 0,06. The impedance technique is used to determine the quantity of solution that penetrates into the pores of the film and, from of the graphic that describes the variations of the capacitance over a period of time, to estimate the solubility and the limit of the saturation that leads to a loss of adhesion. The impedance measurements were performed at open circuit potential after several immersion periods, in the range of the 100 kHz to 10 mHz . The Bode diagrams show clearly a less efficient film protection with the increase of time of exposure in physiologic solution. The maximum value of the impedance |z| obtained, corresponding to the period of the 24 h showing better effectiveness protection, remained around 10⁶Ω · cm² a 0,01 Hz .