Construction Of Robust Superhydrophobic Coating And Its Application In Metal Anticorrosion

The super-hydrophobic coating has aroused increasing attentions in a wide variety of applications such as self-cleaning,anti-corrosin,self-cleaning,oil-water separation,etc,due to its unique wetting property.But the weak stability of super-hydrophobic coating greatly limits its industrial applications.Although numerous techniques have been developed for creating robust super-hydrophobic surfaces in recent years,the harsh preparation conditions,complex steps and high cost of these methods also bring great difficulties for their practical applications.Electrospraying or spraying technique involves the spraying of coating formulations onto substrate surfaces,which possesses quick and convenient deposition of functional coatings onto various substrates,especially for the substrate with large area.Therefore,electrospun/spraying techniques were used to fabricate the superhydrophobic coating in this study.(1)Photopolymerization as a sustainable platform is of high interest in exploring various functional coatings owing to its advantages of high cure speed,room temperature processing,energy-saving,spatial and temporal control over the polymerization.The photocurable formulation can be used as a kind of binder,affording improved adhesion properties between the resultant coating and substrate or low surface energy substance under light exposure.In this study,in comination with the advantages of electrospraying and photocuring techniques,a photoreactive fluorinated copolymer(PFAZ)of 2,3,4,5,5,5-hexafluoro-2,4-bis(trifluorinated methyl)pentyl methacrylate(12FMA)and 2-methacryloyl-oxyethyl-4-azidobenzoate]was designed and synthesized as a low surface-energy additive in the photocurable formulation.It was expected to both reduce the surface free energy and enhance the interactions between PFAZ and electrospayed photocurable layer through decomposing azide groups under UV light.The effects of PFAZ concentration on the microstructure,chemical composition and wettability of the coating were investigated.The results showed that when the PFAZ concentration was higher than 30%,the coating will undergo a dynamic asymmetric phase separation to form a "biphasic continuous network" microstructure surface.The F element was mainly distributed on the outermost layer of the coating.When the PFAZ concentration reached 35%,the static water contact angle of coating was 156.2±2.3 °,exhibiting superhydrophobicity.The resultant superhydrophobic coating demonstrated improved solvent resistance,water impact resistance and self cleaning performance(2)Epoxy resin is well-known as a kind of adhesive.In this study,it was used as a precoating to improve the adhesion between the substrate and the resultant coating.The hydrophobic silica was applied to offer roughness.The PDMS as top-coating was expected to further reduce the surface energy and improve the stability.A stable superhydrophobic coating was successfully prepared on glass,stainless steel,cotton,filter paper and wood surface.The effects of hydrophobic silica and PDMS concentrations on the wettability of the coating were studied.The results showed that when the content of epoxy,hydrophobic silica,PDMS was 200 mg,200 mg and 120 mg respectively,the coating water contact angle/sliding angle of corresponding coating were 156.3±2.6 ° and 2.4± 0.6,exhibiting self-cleaning property.Its superhydrophibicity could be kept even after being immersed in an aqueous solution with pH in the range of 1?10 for 5 days,demonstrating greatlyt improved stability in comparison with the two-component epoxy resin/hydrophobic silica superhydrophobic coating.It indicated that the employment of PDMS as top-coating could greatly improve the stability of the spayed superhydrophobic coating.(3)The corrosion resistance of the superhydrophobic coating in 3.5%NaCl solution was studied by electrochemical workstation.After 7 days of immersion,the corrosion current density of the superhydrophobic coating was slightly increased,which was much lower than bare sample.The results showed the superhydrophobic coating had excellent stability and corrosion resistance.The corrosion resistance of superhydrophobic coating was evaluated by static corrosion weight loss test in 3.5%NaCl solution.The results showed that the corrosion rate of epoxy/hydrophobic silica/PDMS superhydrophobic coating was 91.3%.The surface morphology and chemical composition of the samples were analyzed by SEM and EDS analysis.The corrosion mechanism of superhydrophobic coatings was explored.