Effect of Pre-treatment on Roughness and Hydrophobicity of Electro-Etched Steel with Improved Corrosion Resistance

A hydrophobic steel surface was created by a simple electro-etching technique using a cobalt sulfate bath. The effect of surface pre-treatment on the hydrophobicity and surface roughness was investigated. The wettability and roughness of the surface were determined by water contact angle (WCA) and atomic force microscopy (AFM), respectively. Accordingly, the sample abraded with 800 grit sandpaper followed by electro-etching process was selected as the optimum sample with the highest roughness and WCA (Sa = 28.4 nm, Ra = 35.4 nm, and WCA = 144 ± 1.6°, respectively). The morphology and cross-sectional images of the hydrophobic surface were investigated using field-emission scanning electron microscopy (FESEM). FESEM images showed a micro/nanostructured surface. The resulted hydrophobicity was attributed to the high roughness and overhanging structure obtained through this method. Furthermore, by using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests, the corrosion behavior of the samples was investigated. It was revealed that the surface hydrophobicity improved the corrosion resistance by increasing the polarization resistance (from 726 to 1598 Ω cm2) and decreasing the corrosion current density (from 0.025 to 0.012 mA cm−2). The simplicity of creating a hydrophobic surface with the improved corrosion behavior, the availability, and the low cost of the materials used to develop this approach makes it a proper candidate for large-scale and industrial applications.