Modification of stainless steel by Cu2O coating for hydrophobic applications: a morphological study

Abstract

Wetting properties of the 304 stainless steel indicate a hydrophilic nature. In this study, two methods including Cu2O thin film coating and chemical etching process have been applied on stainless steel substrates in order to fabricate hydrophobic surfaces. Cu2O films were synthesized using spray pyrolysis method at different deposition temperatures and different 2-propanol concentrations. X-ray diffraction (XRD) patterns obtained for the surfaces prepared at different temperatures showed different copper oxide phases well. In addition to XRD results for the samples prepared at different 2-propanol concentrations, the value of optical band gap for these surfaces calculated from UV-Vis spectra confirmed formation of Cu2O structure. Statistical parameters of the surfaces were calculated using atomic force microscopy (AFM) data including rms roughness σ, roughness exponent α and correlation length A similar behaviour was found between water contact angle and local surface slope of thin films. However, in the etching process of steel substrates, the effect of substrate roughness in obtaining water contact angle as high as ≈115° on the Cu2O surface was well established. The morphological properties of these latter surfaces were also studied by scanning electron microscopy (SEM). Generally, knowing statistical information of surface as well as chemical manipulations can be helpful to reach optimal conditions for synthesis of a hydrophobic surface.