Durable hydrophobic Nickel foams via two-step immersion: Stability, corrosion resistance, and oil–water separation

This study presents a two-step immersion method to produce a superhydrophobic film on nickel foams, for oil-water separation applications. The first step involves growing a silver layer to enhance surface micro-roughness, followed by a reduction of the surface energy using stearic acid in the second step. UV-Vis spectroscopy was used to optimize deposition times and monitor any possible film detachment during synthesis. The coating’s structure and elemental composition were characterized through scanning electron microscopy (SEM). Under optimal conditions, a strongly attached hydrophobic silver coating with a water contact angle (WCA) of ~147° was successfully formed. Thermal stability tests showed that the WCA remained above 135° at −15 °C and above 140° at 100 °C, after 50 h of exposure, confirming robust surface durability. The coated foams achieved more than 95% oil/water separation efficiency even after 15 cycles, demonstrating excellent reusability. A comparative evaluation of the corrosion behavior between the hydrophobic and the uncoated nickel foam was carried out using electrochemical impedance spectroscopy (EIS) in a 3.5% NaCl solution. The proposed two step immersion process for the creation of hydrophobic nickel foams proved to be efficient, cost-effective and adaptable. • Simple two-step immersion to fabricate durable hydrophobic nickel foams • Contact angles >135° maintained after 50 h in harsh thermal/chemical tests • Corrosion mechanism shifted from charge-transfer to diffusion control • Oil–water separation efficiency >95% over 15 consecutive filtration cycles • Scalable, low-cost, and environmentally friendly fabrication approach