Corrosion behavior of superhydrophobic surfaces of Ti alloys in NaCl solutions

Superhydrophobic surfaces (SHS) are successfully prepared by 1H, 1H, 2H, 2H-perfluorooctyltrichlorosilane (coded as PFOTS) chemically and physically adsorbed onto the etched Ti alloy substrate. The film formation and its structures are characterized by the measurements of water contact angle (WCA), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The corrosion behavior of the SHS in the NaCl solutions is investigated using the potentiodynamic polarization. The results show that the corrosion resistance of the substrate is improved greatly due to the composite wetting states or interfaces with numerous air pockets between SHS and NaCl solutions. Moreover, it is found that the stability and corrosion resistance of SHS is influenced greatly by the interfacial bonding between PFOTS and the substrate. The strong chemical interfacial bonding (i.e., TiOSi) between PFOTS and the oxidized titanium substrate accounts for a higher stability and much lower corrosion current density as compared by SHS with physically adsorbed PFOTS outerlayer.