Corrosion behaviour of potencially biodegradable ternary alloy Zn-Mg-CaPart of:
Recently, zinc and zinc alloys have been intensively studied as biodegradable materials. One of the most important property, in comparison with magnesium and it is alloys, is the optimal corrosion rate. The values of zinc corrosion rate are in range 0,02 – 0,2 mm/y according to environment of corrosion, which is in good agreement with authors denoting zinc as a suitable material for biodegradable implant fabrication. Another advantage of zinc materials is, that the corrosion process is not primarily connected with hydrogen evaluation as in case of magnesium materials. In this study, electrochemical impedance spectroscopy, potentiodynamic, polarization resistance and immersion tests of as-cast and thermally treated ternary alloys ZnMg0,8Ca0,2 were measured. Also the tests for the cytotoxicity and amount of zinc ion release were performed. The system of thermal treatment was dived into annealing (350°C/24h) and annealing connected with subsequent thermomechanical treatment (extrusion). In case of extrusion, the influence of temperature (150, 200, 300 °C), different extrusion ratios (10:1, 25:1) and the sample surface processing were also observed. All corrosion measurements took place in simulated body fluid at the temperature of 37°C. During the immersion tests the pH values were observed as well because of the potential physiological changes. The change of pH is very often ascribed to the precipitation of the corrosion product and the surface conditions before the exposition. This study helps to evaluate the conditions of the sample processing before the implantation for the optimal response of the organism.