Fabrication Of Surperhydrophobic Surfaces Based On Sol-gel Electrochemistry And Their Applications In Corrosion Protection Of Metals

Wettability,one of the most important properties of solid surfaces,is determined by the rough structure and chemical compound.Superhydrophobic surface with water contact angle larger than 150° and sliding angle less than 10° has attracted numerous attention in both industrial and academic area.The superhydrophobicity can be found everywhere in nature,such as the water on the leaf can easily roll off the surfaces and water strider can walk on the water surface without its legs wetted.Intensive researches show that the microstructure of leaf is consisted of two-scale roughness,e.g.nano-scale fine structure existing on the micro-scale rough structure.The hierarchical micro/nano roughness structure and the epicuticular wax crystalloids with low surface energy are responsible for the final superhydrophobicity.Inspired by this,two different routes are developed to construct superhydrophobic surfaces:one is to make the required rough structure from the low surface energy material;another is to modify the rough surface with low energy compound.Until now,various methods have been developed to fabricate the superhydrophobic surfaces,including hydrothermal treatment,etching,chemical vapor deposition,electrodeposition,electrospinning and so on.Among these,electrodeposition technique with controllable and repeatable has attracted extensive attention in the application fields of electroanalysis,biosensors,fabrication of superhydrophobic surface,corrosion protection of metals,etc.In this research,electrodeposition technique was used to construct superhydrophobic surface for the corrosion protection of metal substrates;by introducing inhibitors into the porous micro/nano structure of superhydrophobic film,active corrosion protection was achieved;polymer with low energy surface was introduced to construct abrasion-resistant superhydrophobic surface;abrasion-resistant,hot water-repellent and self-cleaning superhydrophobic surfaces were prepared by the electrophoresis of superhydrophobic silica synthetized through moderate process into the robust and porous electrodeposited sol-gel films.The main context is listed as followed:(1)Electrodeposition of superhydrophobic sol-gel film and the study of its performance."One-step" or "two-step" method was used to fabricate superhydrophobic surface on the mild steel.The corrosion protection performance of superhydrophobic film coated substrates were investigated by monitoring the change of contact angle,iron dissolution determination and EIS measurements.The results show that the superhydrophobic film can effectively improve the anticorrosion performance and reduce the corrosion rate.Compared with the "one-step" superhydrophobic surface,the latter shows an improved mechanical durability and reparability to heat-induced destruction.(2)Construction of superhydrophobic film with active corrosion protection and the study of its performance.Electrochemically generated SiO2(e-SiO2)films are used as inhibitors container to fabricate surfaces with active anticorrosion performance.Two different routes were developed to incorporate corrosion inhibitors in view of the different solubility of inhibitors in the low surface energy solution.The cerium salt can forms oxides/hydroxides on the silica surface therefore was embedded into superhydrophobic films by a step-by-step method.For organic inhibiting agents,e.g.BTA,prone to leaching into the low-surface-energy modifying precursor,one-step electrodeposition was applied for the incorporation of BTA.The release kinetics of BTA from superhydrophobic film indicates that the corrosion inhibition role of the BTA-encapsulated superhydrophobic film is induced by the corrosion process itself.Both EIS and SVET measurements show that introduction of inhibitors,irrespective of types,generates an improved anticorrosion performance.(3)Fabrication of robust superhydrophobic surfaces based on polymer and superhydrophobic silica and its performance.Firstly,the polymer with low surface energy(polydimethylsiloxane:PDMS)was used as the modifier of electrodeposited SiO2 films.Less amount of PDMS is not beneficial to the superhydrophobicity and abrasion resistance,while excess PDMS would result in the reduction of roughness of e-SiO2.Abrasion resistant superhydrophobic SiO2 film was obtained only when proper amount of PDMS was used as modifier.Results show that PDMS can effectively cross-link the e-SiO2 films,which reduce the abrasion-induced destruction to the micro/nano structure.Secondly,the home-made water-repellent silica was embedded into the porous e-SiO2 films by an extra drive.e.g.electrophoresis.Results show that the superhydrophobic silica(SH-SiO2)particlesfill in the porous network through the whole-thickness of rigid e-SiO2 film,and the obtained films was endowed with both the rigid e-SiO2 skeleton and the superhydrophobicity of SH-SiO2.Compared with the two-step superhydrophobic film in(2),the aboved two prepared superhydrophobic films show an improved abrasion resistance.In addition,the SH-SiO2 embedded superhydrophobic film exhibits excellent repellency to hot water,heat destruction and self-cleaning performance either in air or oil.