The Effect of pH Value of a Simulated Physiological Solution on the Corrosion Resistance of Orthopaedic Alloys.

: Metals and alloys used in orthopaedics and dentistry are exposed in vivo to various agents and environmental conditions. One of the important factors that determine the corrosion behaviour of metallic biomaterials is the pH of the environment. The corrosion resistance of stainless steel 316L (Fe/Cr18/Ni10/Mo3), titanium and titanium alloy Ti-6Al-4V (Ti90/Al6/V4) was studied in terms of their electrochemical properties and biodegradation in simulated physiological solutions of different pH values (4.5, 6.5, 7.5 and 8). The electrochemical characteristics of individual metal components were also investigated using cyclic voltammetry, linear polarization and potentiodynamic polarization methods. The concentration of dissolved metal ions released during 32 days immersion under simulated physiological conditions was determined by inductively coupled plasma mass spectroscopy. The corrosion behaviour of stainless steel 316L is strongly affected by the pH of the physiological solution in the range from 4.5 to 8.0. The corrosion resistance was enhanced at higher pH and the concentrations of released metal ions lower. The behaviour of titanium and its alloy however is almost independent of the pH.