Fabrication Of Superbydrophobic Surface And Its Corrosion Behaviors In Sea Water

Inspired by the superhydrophobic phenomena in the nature, two methods for the preparation of superhydrophobic surface (SHS) on Ti6A14V and copper substrates were developed. The related properties and the structures of the fabricated superhydrophobic surfaces were investigated. And then, form three aspects, i.e., the influence of surface roughness/interfacial bonding/micro-structures of the film on the corrosion resistance, the corrosion behaviors of the SHS in sea water were investigated. The main conclusions and contents are listed in the following.1. Rrecent development of superhydrophobic phenomena in the nature and the fabrication methods for SHS were summarized. The potential applications of SHS in the field of corrosion resistance and the anti-corrosion mechanisms were also reviewed.2. The correlation between the surface roughness and the corrosion resistance of SHS were investigated. SHS or hydrophobic surfaces on copper substrates were prepared by a two-step method. Firstly, a novel etching reagent system (5mM HNO3-1.2mM CTAB) was proposed to fabricate different surface roughness by controlling the etching time. Secondly, the surface energy was lowered by grafting with1H,1H,2H,2H-perfluorodecanethiol (PFDT). Corrosion experimental results showed that the corrosion rate increased as the surface becoming rougher for bare copper substrates; the corrosion rate decreased as the surface becoming rougher for SHS or hydrophobic surfaces. This suggests that the roughness plays a positive role in corrosion resistance for SHS.3. The correlation between the interfacial bonding and the corrosion resistance of SHS were investigated. SHS on HF or HF/H2O2treated titanium alloy substrates were successfully fabricated and the corrosion resistance of SHS was estimated by potentiodynamic measurements. Corrosion experimental results indicated that SHS on HF/H2O2treated substrate was more resistant to corrosion as compared with SHS on HF etched substrate. The improvement were attributed to the following two aspects, on one hand, a layer of TiO2acting as a corrosion barrier was generated under the treatment of H2O2; on the other hand, the generated TiO2was supposed to induce the chemical interfacial bonding between the low surface energy molecules (1H,1H,2H,2H-perfluorooctyltrichlorosilane PFOTS) and the HF/H2O2treated surface.4. The correlation between the microstructures of the grafted low energy molecules and the corrosion resistance of SHS were investigated. Two SHS coded as Cu-PFDT and Cu-MPTMS-PFDS were prepared. The tail/head groups of the two films were the same and the bulk chain was different. The interchain polysiloxane microstructures for Cu-MPTMS-PFDS were also supposed to be effective in enhancing the corrosion resistance of the film by delaying the penetration of corrosive medium, such as water and the dissolved ions.