Flower-like Superhydrophobic Surfaces Fabricated on Stainless Steel as a Barrier against Corrosion in Simulated Acid Rain

Abstract

Functionalisation of the metal surface of low-carbon ferritic stainless steel (from hydrophilic to hydrophobic properties) was achieved by flower-like hierarchical structures on a steel substrate prepared by a low-cost immersion method. The flower-like structured hydrophobic layers on the steel substrate were obtained by immersing the samples in an ethanolic solution of stearic acid with the addition of various concentrations of expired vitamin E ((+)α-tocopherol). The stability and corrosion-inhibiting effect of the hierarchically structured (such as natural cornflower) hydrophobic layers were studied systematically during short and long immersion tests, 120 h (five days) in an acidic environment (pH = 3) using potentiodynamic measurements, electrochemical impedance spectroscopy and chronopotentiometry. The surfaces of the samples, their wettability, surface morphology and chemical composition were characterised by contact angle measurements, SEM, ATR-FTIR and EDAX. After 120 h of immersion, the inhibition efficiency of the flower-like structured hydrophobic layers on the steel substrate in the selected corrosion medium remained above 99%, and the hierarchical structure (flower-like structure) was also retained on the surface.