Fabrication of superhydrophobic ti surface by thermal oxidation and its anticorrosion property

Abstract

Ti and its alloys, due to their good stability and high strength-to-density ratio, have been widely used in many industry fields, such as aviation, navigation, biomedical devices, etc. It is quite necessary to improve their performance against corrosion of water pollution or other corrosive mediums in these fields. The process of thermal oxidation is an effective way to enhance their corrosion resistance while high-temperature oxidation is usually thought to have detrimental effects. However, the porous structure caused by high-temperature oxidation is found to be beneficial for preparation of superhydrophobic surface, which has gotten extensive application in improvement of metals' antcorrosion ability. In this study, a rough surface with hierarchical micro- and nano-structures was formed on Ti by a heat treatment process in atmospheric environment at 1000°C for 1 h. The following air-cooling process separated the flaky yellow oxide layer formed on Ti plate during the oxidation from the substrate and a grey porous substrate (TO) was obtained. Furthermore, TO was modified with n-octadecyltrichlorosilane (OTS), leading to the formation of superhydrophobic Ti surface (TO-OTS). The TO-OTS film exhibited a static contact angle of 166.0° and a rolling angle of 2.0° for 5 μL water droplets. The as-prepared film was characterized by XRD, FE-SEM, XPS and contact angle measurements. The results indicated that dual-scale roughness leaved by thermal oxidation endowed TO-OTS with excellent non-sticking superhydrophobicity and durability, even for some corrosive liquids including salt solution and acidic and alkali solutions at different pH values. By means of immersion test, TO-OTS displayed great non corrodibility against HF solution, with a protective mirror-like air film formed above it. Moreover, based on potentiodynamic polarization measurement in 3.5%NaCl solution, the corrosion resistance of TO-OTS was proved to have a significant enhancement with a protection efficiency of 99.1%. This is a facile method for preparation of large-scale or complex shaped superhydrophobic surfaces without requirement of expensive instrument, which may provide an effective protection for Ti under harsh environment.