In situ hydrothermal synthesis of oxide film on NiTi for improving corrosion resistance in Hanks’ solution

Hydrothermal treatment was used to grow oxide film on NiTi to improve corrosion resistance. The film was smooth and about 56 nm thick. X-ray photoelectron spectroscopy indicated that the surface atomic ratio Ni/Ti was reduced from 0.30 to less than 0.01 after treatment. The film was composed of Ti oxides, with a small amount of Ni. After hydrothermal treatment, corrosion resistance in Hanks’ solution was significantly increased as indicated by electrochemical impedance spectroscopy and polarization tests, and crevice corrosion test.