Nano Structure of the Rust Formed on an Iron-based Shape Memory Alloy (Fe–Mn–Si–Cr) in a High Chloride Environment

Abstract

The corrosion resistance of an Iron-based shape memory alloy (28 Mn: Fe–Mn–Si–Cr) was estimated by using wet and dry corrosion test. The structure of the rust formed on the alloy was examined via EELS (Electron Energy Loss Spectroscopy) using TEM (Transmission Electron Microscopy) analysis. The electrochemical behavior of the 28 Mn alloy was investigated via EIS (Electrochemical Impedance Spectroscopy). The 28 Mn alloy showed a much higher corrosion resistance than SM (carbon steel) in wet and dry corrosion test. In EIS measurement following the corrosion tests, the 28 Mn alloy exhibited a much larger value of corrosion resistance (Z_1mHz) as compared to SM, which can be attributed to rust formation. TEM analysis indicated that the inner rust was composed of Mn-rich, Cr-Si rich and interface layer. The corrosion resistance was primarily dependent on the Cr-Si rich layer, and further supported by the Mn rich layer. It was found that the 28 Mn alloy could maintain a protective rust layer composed of effective elements in the wet and dry environment.