Preparation And Properties Of Polyurethane/Graphene Composite Anticorrosive Coating On Carbon Steel Surface

Corrosion is the degradation of metals and alloys by chemical or electrochemical methods,which has a certain impact on economy,safety and health.This is a huge challenge to society,industry and citizens.A common solution to this type of problem is to use a barrier to limit or prevent the transport of corrosive or oxidizing substances from the environment to the target.In recent years,the application of graphene in anticorrosion has been extensively studied.In this paper,humic acid functionalized graphene aqueous dispersion?HGP?was prepared by electrochemical exfoliation method.A graphene/waterborne polyurethane?HGP/WPU?composite coating was prepared using waterborne polyurethane?WPU?as a film-forming material and HGP as a filler.In addition,styrene-maleic anhydride copolymer functionalized graphene?SGP?was used as a stabilizer to prepare graphene-polyaniline?SGP-PANI?composites by in-situ polymerization.A graphene-polyaniline/waterborne polyurethane?SGP-PANI/WPU?composite coating was prepared by blending with aqueous polyurethane.The anti-corrosion ability of the two composite coatings was investigated by using the AC impedance test and the Tafel polarization curve test.In addition,if the addition of nano-SiO₂ and several corrosion inhibitors can improve the anti-corrosion performance of the composite coating were also investigated.The morphology and structure of HGP and SGP-PANI were characterized by SEM,TEM,XPS,FTIR,Raman,XRD and UV.The results showed that graphene was successfully functionalized by humic acid withing good water dispersion stability.Polyaniline was successfully modified on the surface of HGP,and the zeta potential showed that the SGP-PANI aqueous dispersion was stable.The SEM images of the fracture surface of HGP/WPU and SGP-PANI/WPU composite coatings show that HGP,SGP-PANI and WPU are successfully combined.HGP accounts for 0.05%of WPU and HGP has the best dispersion uniformity in the coating.Adhesion test results show that the addition of HGP and SGP-PANI does not weaken the adhesion of WPU to carbon steel.The addition of HGP can improve the corrosion resistance of WPU coating,and the composite coating achieves the best anti-corrosion effect when HGP accounts for0.05%of WPU.The addition of nano-SiO₂ can effectively increase the anti-corrosion performance of the composite coating,and the optimum addition amount is 4%of the total system.The addition of sodium metavanadate and ammonium fluorotitanate can significantly improve the corrosion resistance of the composite coating.The addition of sodium molybdate and phytic acid does not improve the corrosion resistance of the composite coating.The addition of SGP-PANI as a filler to the WPU also improves the corrosion resistance of the coating.The composite coating has the best corrosion resistance when the SGP-PANI content is 0.6%.The anti-corrosion effect of the composite coating modified by nano-SiO₂ is enhanced,and the corresponding anti-corrosion ability of the composite coating is 4%of the total system.The investigation results of corrosion inhibitors show that the addition of sodium molybdate and ammonium fluorotitanate can enhance the corrosion resistance of the coating,and the optimum addition amount is 0.06%of the total system.The addition of sodium metavanadate and phytic acid does not effectively improve the corrosion resistance of the composite coating.