Effects of water plasma immersion ion implantation on surface electrochemical behavior of NiTi shape memory alloys in simulated body fluids

• Published in: Applied surface science Vol. 253; no. 6; pp. 3154 - 3159
• Main Authors: Liu, X.M., Wu, S.L., Chu, Paul K., Chung, C.Y., Chu, C.L., Yeung, K.W.K., Lu, W.W., Cheung, K.M.C., Luk, K.D.K.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-01-2007; Elsevier Science
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Electrochemical impedance spectroscopy; Exact sciences and technology; NiTi; Physics; Plasma immersion ion implantation; Water plasma immersion ion implantation; Water plasma immersion ion implantation; NiTi; Plasma immersion ion implantation; 82.47.Wx; Electrochemical impedance spectroscopy; Water; Ion implantation; Shape memory alloy
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2006.07.008

Water plasma immersion ion implantation (PIII) was conducted on orthopedic NiTi shape memory alloy to enhance the surface electrochemical characteristics. The surface composition of the NiTi alloy before and after H
2O-PIII was determined by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) was utilized to determine the roughness and morphology of the NiTi samples. Potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS) were carried out to investigate the surface electrochemical behavior of the control and H
2O-PIII NiTi samples in simulated body fluids (SBF) at 37
°C as well as the mechanism. The H
2O-PIII NiTi sample showed a higher breakdown potential (
E
b) than the control sample. Based on the AFM results, two different physical models with related equivalent electrical circuits were obtained to fit the EIS data and explain the surface electrochemical behavior of NiTi in SBF. The simulation results demonstrate that the higher resistance of the oxide layer produced by H
2O-PIII is primarily responsible for the improvement in the surface corrosion resistance.