Corrosion Behavior Assessment and Comparison of UNS S31603 Stainless Steel, Nickel-Titanium Shape Memory Alloy, and Al2Cr5Cu5Fe53Ni35 High-Entropy Alloy in Biomedical Environments
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Electrochemical characterization was performed on near-equiatomic nickel-titanium shape memory alloy (SMA), Al2Cr5Cu5Fe53Ni35 high entropy alloy (HEA), and UNS S31603 stainless steel to assess and compare the corrosion behavior and resistance of the material in simulated biomedical environments. A simulated bio-fluid (SBF) electrolyte was used to study the chemical and temperature-controlled parameters that the alloys experienced when they were exposed to corrosion conditions. Electrochemical testing, such as EIS and LPR tests, was performed to observe the response of the material under a range of conditions. Cyclic polarization tests were performed on all three materials to determine and compare passive to active behavior. Different performance vs. conditions correlations were described by using high-resolution surface techniques such as SEM following electrochemical testing resulting in some interfacial active-passive mechanisms.Materials selection in the biomedical sector has become a critical area of research, and the care and treatment of patients need to be continuously improved as technology advances. There is a broad range of such applications for metals in the current state of the industry, including dentistry and orthodontics, surgical tools, implants, stents, and bone staples and screws. Each of these applications entails a unique environment within the human body, and as new alloys are developed, it is crucial to understand their degradation behavior and response when exposed to the harsh conditions found throughout biomedical applications.For this study, three materials were selected in order to compare corrosion behavior UNS S31603 stainless steel was chosen as a benchmark material, as it is commonly used throughout the biomedical industry for its biocompatibility and stable performance when exposed to biological environments. UNS S31603 stainless steel finds wide usage due to its good mechanical properties, versatility in shaping for different applications, and cost in comparison to other alloys. However, its chromium and nickel content necessitate a high degree of corrosion resistance to improve its longevity and control and prevent the release of potentially harmful ions into the body. Additionally, studies have shown the corrosion resistance of UNS S31603 stainless steel in biological environments is highly sensitive to surface finish, leading to more complex manufacturing methods [1, 2]. The NiTi SMA used in this study was a 55.8 wt.% Ni-rich NiTi alloy. The passive film formed on NiTi SMAs has been shown to consist of predominantly titanium oxide (TiO2), [3] which has been shown to be stable and protect against the oxidation of Ni, making it another good choice for biocompatible implant material. The non-negligible Ni-content in these SMAs has raised some concerns about potentially harmful nickel ion release into the body, necessitating careful control of the alloy content and surface finish in order to preferentially form the biocompatible titanium oxide passive layer.
