Electrochemical impedance behavior and corrosion resistance of amorphous 316-type stainless steel microfibers in saline environment

The resistance of commercial stainless steel (SS) types in harsh environments is problematic because of the breakdown of the passive chromium oxide layer. This study aims to improve the corrosion resistance and passivation properties of commercial SS by producing fully amorphized 316 SS microfibers with multi-nozzle melt-spinning. Electrochemical tests in 3.5 wt% NaCl shows a low current density of 0.77 × 10–5 A cm–2 under ambient conditions, which increases slightly to 1.0 × 10–5 A cm–2 as the temperature rises to 50 °C. Sample electrochemically tested at 25°C also shows a current density at the level of 10–4 A cm–2 with long-term stability, and minor metastable pitting due to metal-Cl─ ion interactions is observed for the sample at 50 °C until 1.5 V. Electrochemical impedance spectroscopy before and after polarization at 50 °C shows an increase in both charge transfer resistance and double-layer admittance, suggesting double-layer formation on the outer surface due to Cl─ ion accumulation. Cross-sectional investigation by scanning transmission electron microscopy–electron energy loss spectroscopy corroborates the homogenous bulk composition and Fe-rich, Ni and Cr-containing amorphous oxide (<200 nm), both of which contribute to the corrosion resistance and passivation properties compared to nanocrystalline SS counterparts.