Corrosion behavior of NiTi alloys in chloride environments with different concentrations

Abstract

© 2026 The Authors.NiTi alloys are well known for their Shape Memory Effect (SME) and are widely used in various fields, including engineering and biomedical applications such as stents. In this study, the corrosion behavior of two solution-treated NiTi alloys with distinct microstructures, martensitic (Ti55Ni) and austenitic (Ti56Ni), was investigated in 0.9% and 3.5% NaCl solutions. The samples were subjected to immersion tests in accordance with ASTM G31–72 for up to 720 h, with monitoring of mass loss, pH variation, and surface characterization by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), along with X-ray diffraction (XRD) to evaluate the post-corrosion structural condition. Electrochemical tests (OCP and Linear Potentiodynamic Polarization) were also conducted to complement the assessment of alloy performance. The results showed low mass loss for both alloys; however, distinct corrosion responses were observed depending on microstructure and testing methodology. The austenitic alloy exhibited lower corrosion rates in immersion tests, whereas the martensitic alloy showed more favorable electrochemical behavior, characterized by more noble corrosion potentials and lower corrosion current densities. Overall, the corrosion behavior of NiTi alloys was found to depend on both microstructure and chloride concentration, with different trends observed under immersion and polarization conditions.

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