Effect of pH on the polarization behavior of Zr₆₅Al_7.5Ni₁₀Cu_17.5 amorphous alloy in a phosphate-buffered solution

For the biomedical use of amorphous alloys, the effect of pH on the polarization behavior of Zr₆₅Al_7.5Ni₁₀Cu_17.5 amorphous alloy was evaluated in phosphate-buffered solutions with and without chloride ion. In the solution without chloride ion, the corrosion resistance at open-circuit potential decreased with a decrease in pH. The open-circuit potential was ennobled with a decrease in pH by the acceleration of a cathodic reaction. However, the open-circuit potential was not changed by chloride ion, and the pitting potential was not changed with the decrease in pH. Then, the open-circuit potential was always less noble than the pitting potential. Therefore, the pitting-corrosion resistance of the zirconium-based amorphous alloy decreases with a decrease in pH due to the shift of the open-circuit potential. However, pitting corrosion does not occur spontaneously with a decrease in pH. (C) 2000 Elsevier Science Ltd. All rights reserved.