Effect of post treatment parameters on corrosion resistance of Ti-13Nb- 13Zr coated with hydroxyapatite via electrophoretic deposition

Abstract

Recently, applications of Ti-13Nb-13Zr alloy have been widely increased in biomedical fields due to its excellent biocompatibility and mechanical properties. However, its corrosion resistance is still a matter of concern when it is implanted inside human body. Many attempts have been done to enhance its corrosion resistance by using hydroxyapatite coating. This study includes two major directions; firstly calcium phosphate was electrophoretically coated on Ti-13Nb-13Zr surface in order to improve its corrosion resistance. Sintering post treatment was then conducted to the coated samples in order to transform the deposited layer from dicalcium phosphate dehydrated (DCPD) phase to the hydroxyapatite crystalline (HA) phase. The effect of two different sintering post-treatment parameters including time and temperature have been experienced on the corrosion potential of calcium phosphate coated substrate. Full factorial experimental designs followed by Response Surface Methodology (RSM) were employed for planning and analyzing the experimental results. Time and temperature of sintering post-treatment were considered as independent variables while corrosion potential is accounted as a response variable. Empirical models were successfully developed to predict amount of corrosion potential by using design of experiment (DOE) software. Experimental results show that the effect of sintering temperature is more significant than the sintering time. Moreover the results indicate that high corrosion potential is obtained under sintering conditions at (Time = 90 minutes, Temperature = 700° C). Finally, the electrophoretic deposition method exhibits a relatively uniform HA coating layer and free of crack.