Surface Modification of Gr.91 Steel via Electrochemical Etching and Its Effect on Surface Properties

Abstract

We introduce a process for modulating the wettability of Mod.9Cr-1Mo (ASME Gr.91) steel surfaces by forming microstructures. Surface modification was achieved through electrochemical etching, where experiments were conducted by varying applied voltage, reaction time, and electrolyte concentration. Without additional processes, such as hydrophobic coatings, the surface of the specimens was modified to hydrophobic through electrochemical etching. Post-process changes in surface morphology were analyzed using SEM images and surface roughness obtained via confocal laser scanning microscopy. The alterations in wettability on the modified surface were confirmed by measuring the static contact angle and observing the droplet behavior, illustrating how the droplet spreads and retracts upon colliding with the surface. The contact angle of the bare Gr.91 steel surface was 89.3°, while the modified surface reached a maximum of 143.8°. Based on these analyses, we confirmed that a simple yet effective electrochemical etching process can impart a durable hydrophobic characteristic to Gr.91 surfaces.