High Voltage Anodization of a NiTi Shape Memory Alloy

In order to improve the corrosion resistance of a NiTi shape memory alloy, thick oxide films were fabricated on the surface by an anodic oxidation process. The microscopic observation showed the films had a porous nature and the structural analyses indicated that the films are amorphous. From the chemical analyses, the oxide films mainly contained titanium as metal component, the nickel content of the oxide films depends on pH of the electrolyte and anions could be incorporated from the electrolyte into the films. The asymmetrically rectangle waveform was effective to increase the density of the films. The electrochemical technique showed that the corrosion resistance of the anodised films could improve the resistance against localized corrosion of NiTi.