| Coating protection is one of the key technologies to improve the corrosion resistance of metals.The addition of super-hydrophobic nanofillers can improve the surface roughness of the coating and enhance the hydrophobic properties of the coating,which is very beneficial to inhibit the corrosion particles from attacking the metal.Using hydrophilic nano titanium dioxide(TiO2)and graphene oxide(GO)as raw materials,different types of amino-terminated polysiloxanes were used for superhydrophobic modification.The effect of two superhydrophobic fillers on the physical and chemical properties of each composite coating was discussed to enhance the physical hydrophobic anticorrosion ability of the coating and provide a new idea for the development of coatings with better performance.The specific research contents and results are as follows:(1)The superhydrophobic TiOO2-POSS powders were prepared by using y-glycidyl ether oxypropyltrimethoxysilane(KH-560)as a coupling agent by modifying nano-titanium dioxide(TiO2)was modifiled by aminopropyl isobutyl polypolyhedron siloxane(POSS-NH2).The chemical component and structure,surface micro-morphology and hydrophobicity of the products were characterized by fourier transform infrared spectroscopy(FTIR),x-ray diffractometer(XRD),thermogravimetric analyzer(TGA),scanning electron microscope(SEM)and water contact angle tester(CA),et al.The results showed that,compared with rutile TiO2 powder,the thermal stability of the successfully synthesized TiO2-POSS powder was significantly improved,while the microstructure changed obviously and the surface roughness increased,showing superhydrophobicity with a water contact angle of 164.5°.The dispersion stability of different solvents was toluene>DMSO>DMF>ethanol,and TiO2-POSS had good dispersibility in ethanol in a short time(2 h),which could meet the experimental conditions required for the subsequent coating preparation process.(2)The synthetic superhydrophobic TP was used as the pigmentfiller and the waterborne epoxy resin as film-forming material,the hydrophobic TP/WEP composite coatings with different filler content ratios were prepared by simple mechanical mixing.The surface morphology and static water contact angle of the composite coating were studied by SEM,ultra-depth microscope and CA test.Meanwhile,the wettability,physical and mechanical properties and anti-corrosion protection for metal substrates of the composite coatings were investigated by water absorption,adhesion,ultraviolet radiation,electrochemical impedance spectroscopy and salt resistance.The experimental results showed that nano-scale rough structured TP can fill the original defects in the pure water-based epoxy resin matrix,build a micron-scale(1-50?m)uneven surface structure,adsorbed air and form an air cushion,which can enhance the water-resistance of the coating and reach the degree of hydrophobic.When the TP filler content was 0.5 wt%,the compatibility with resin is the best,and the static water contact angle was 107.3°.Various composite coatings were maintained at about 100?m with fir-st-level adhesion,and 6H hardness.TP/WEP coating did not change greatly in static water contact angle under long-term ultraviolet radiation and had excellent ultraviolet durability.The contact angle of 0.5 wt%TP/WEP coating changed only 0.9°after prolonged UV light exposure.0.5 wt%TP/WEP coating has the best corrosion resistance.And the impedance modulus at the initial stage of immersion reached 4.41 ×109 ?·cm2,which was at least an order of magnitude higher than other coating systems.Even after 30 days of immersion,the impedance modulus only decreased by one order of magnitude,which was about two orders of magnitude higher than the value of |Z|0.01 Hz(WEP,30 d),and there were only a few rust spots after soaking in 3.5%NaCl solution for 720 h.(3)The terminal amino polydimethylsiloxane(H2N-PDMS-NH2)was first reacted with isophorone diisocyanate(IPDI),and then used to hydrophobically modified graphene oxide(GO).FTIR,TGA,Raman,SEM,and CA tests showed that the PDMS-IPDI@GO powder was successfully synthesized,and the thermal stability was significantly improved compared to pure GO.The water contact angle of the PDMS-IPDI@GO powders was 158.2°,showing excellent superhydrophobicity.Then it was mixed with the optimal ratio of TP and WEP emulsions to prepare a strong hydrophobic composite coating by brush coating,and the physical and chemical stability and corrosion resistance of the coating were studied.The experimental results showed that the filler in the TP@PDMS-IPDI@GO/WEP composite coating has good dispersion compatibility with the epoxy matrix,has a dual micro/nano rough surface morphology,thus exhibits excellent hydrophobic properties.After being exposed to various harsh conditions such as hot water,liquid nitrogen,strong acid to strong alkali system,the coating still maintained excellent chemical stability,and the hydrophobic properties had not chang much.Also,the resulting coating could undergo mechanical durability experiments such as sandpaper wear without significant change in its hydrophobic properties.The composite coating exhibited superior corrosion resistance in a 3.5%NaCl solution.The impedance modulus|Z|0.01 Hz when immersed for 1 d was 1.23×1010 ?·cm2,which was approximately two orders of magnitude higher than that of a blank WEP coating.The salt water resistance experiment also confirmed that the TP@PDMS-IPDI@GO/WEP composite coating has the better corrosion protection effect. |
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