A Study on Functional Hydrophobic Stainless Steel 316L Using Single-Step Anodization and a Self-Assembled Monolayer Coating to Improve Corrosion Resistance

Abstract

Stainless steel fabricated using chromium is widely being used in various industries due to its superior corrosion resistance compared to light metals such as aluminum, titanium, and magnesium. However, despite its excellent properties, a problem of poor corrosion resistance in harsh environments remains. In this study, an economical and environmentally friendly anodizing process was applied to the surface of stainless steel (SUS 316L) to create porous nanostructures to improve its water-repellent properties. In these experiments, voltages of 30, 50, 70, and 90 V were applied to stainless steel for 3 h to form an oxide film, prior to immersion in 0.1 M phosphoric acid for 10 min to expand the oxide pores. In addition, the change of the oxide structure was observed through field-emission scanning electron microscopy (FE-SEM). In terms of the contact angle, hydrophilicity was observed at applied voltages of 70 and 90 V, in which a porous film was formed; the best water repellency was observed at a 90 V applied voltage, after the application of an FDTS (1H,1H,2H,2H-perfluorodecyltrichlorosilane) coating, a self-assembled monolayer. Finally, the corrosion behavior of a hydrophobic specimen was tested using potentiodynamic polarization (PDP) experiments. The hydrophobic SUS 316L alloy subsequently displayed improved corrosion resistance in a 3.5 wt% NaCl solution.