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. The room temperature sample also shows a low passivation current at the level of 10–4 A cm–2 with long-term stability, and no pitting is observed for all the samples until 1.5 V. The sample polarized at 37°C shows the smallest bulk resistance (~ 1400 Ω cm2) and the largest double-layer capacitance (28.6 µF cm–2), where large amounts of salt accumulation on the surface creating a passive layer on the microfibers were detected by energy dispersive X-ray (EDX)–scanning electron microscopy. Cross-sectional investigation by EDX-scanning transmission electron microscopy corroborates the homogenous bulk composition and Fe-rich, Ni and Cr-containing amorphous oxides, both of which contribute to the enhanced corrosion and passivation properties compared to commercial SS counterparts in the literature.