Enhanced Electrochemical and Corrosion Behavior of Amorphous 316-Type Stainless Steel Microfibers in Saline Environment

Abstract

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 reports fully amorphized 316 SS microfibers using a customized multi-nozzled melt-spinning technique. Electrochemical tests in 3.5 wt.% NaCl shows a high corrosion resistance with an annual corrosion rate of less than 60 µm year–1 under ambient conditions, which increases slightly as the temperature rises to 50 °C. Sample electrochemically tested at 25 °C also shows a low passivation current at the level of 10–4 A cm–2 with long-term stability, and only minor pitting due to metal - Cl─ ion interactions is observed for the samples until 1.5 V. During electrochemical impedance spectroscopy before and after polarization, the increase in both charge transfer resistance and double-layer capacitance after polarization at 50°C indicates a double-layer formation on the outer surface due to Cl─ ion accumulation. Large amounts of salt particles on the surface of the microfibers after removing from the solution and drying were detected by energy dispersive X-ray – scanning electron microscopy. Cross-sectional investigation by EDX-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 enhanced corrosion and passivation properties compared to commercial SS counterparts in the literature.

Keywords: Corrosion, Stainless Steel, amorphous, Electrochemistry, microfibers