Aqua Barrier: Polypropylene/Stearic Acid-Infused Zn-ZnO-Cu Multilayer Superhydrophobic Coatings on Steel for Enhancing Anti-Microbial and Anti-Corrosion Efficiency

This study investigates the enhancement of anti-microbial efficiency, hydrophobicity, and corrosion resistance, by depositing a multilayer Cu and Zn/Zno superhydrophobic (SH) coating modified with polypropylene/stearic acid (PP/SA) on steel. The electrodeposition of Cu and Zn on steel results in a unique leaves and cotton-like structures, increasing the hydrophobicity with a contact angle(CA) of 157°, up from 24° for bare steel. Further modification with polypropylene and stearic acid (PP/SA) maximises the contact angle to 167° and minimises the F sl value to 1.34%, resulting in improved surface energy reduction and increased hydrophobicity. The anti-microbial efficiency of the polypropylene-stearic acid-modified Zn-Cu SH coating demonstrates a remarkable zone of inhibition of 30 mm, which is 300 times more effective than bare steel against E.coli Bacteria. The micro- and nano-scale roughness of the SH surface creates a challenging environment for microbial adhesion, reducing the risk of contamination by minimising contact area and inhibiting attachment. Corrosion resistance, evaluated through electrochemical impedance spectroscopy (EIS) and open circuit voltage (OCV), revealed exceptional performance, a corrosion rate of 0.00153 mm year −1 with a polarisation resistance of 12200 Ω.cm 2 , and a charge transfer resistance of 600000 Ω. cm 2 . The nanostructured coating traps air to minimise contact area, providing superior corrosion protection. This study demonstrates that the Cu-Zn SH coating modified by PP/SA significantly enhances anti-microbial, hydrophobic, and corrosion-resistant properties, providing a promising approach for steel surface protection.