Reactive Element‐Effect Optimized Ni–Cr–W–Al Alloy for Fabricating Robust and Fluorine‐Free Superhydrophobic Coating on Al Alloy

This study develops a readily implementable surface modification technique for Al alloys by combining electroplating alloy films with depositing stearic acid to make a durable superhydrophobic coating. Selecting Al as anode for electroplating innovatively, the introduction of Al element improves the adherence and roughness of the coating through a principle identical to the reactive element (RE) effect. Al can be preferentially combined with oxygen to reduce the partial pressure of oxygen, inhibiting outward diffusion and oxidation of the electroplated alloy components, reducing the defects formed by the outward diffusion of the metal elements and the accompanying porosity and cracks. Besides, the dense and stable nature of the oxide film formed by RE effect can better protect the Al alloy substrates from oxidation. It is shown that the crystallinity and oxidation resistance of the alloy is significantly enhanced by the RE effect. Notably, the champion water contact angle has reached 162° ± 0.7°, and a significant reduction in surface porosity is observed. This research has the potential to provide a simplified fabrication process of Ni–Cr–W alloy and pave the way for the development of durability of superhydrophobic film.