Study Of Characteristics And Anticorrosion Mechanisms Of The Graphene-Based Layered Nanomaterial Modified Waterborne Coatings

The application and storage process of conventional organic coatings involves the emission of toxic volatile organic compounds?VOCs?into atmosphere,which continuingly damaging the environment.In recent years,more and more environmentally friendly water-based coatings have drawn to people's attention.However,the film-forming process of water-based coatings is prone to form pores,resulting in poor barrier effect.Graphene has many remarkable characteristics,such as size effect,high hydrophobicity and conductivity.The unique two-dimensional layered crystal structure,high anisotropy and good controllability of graphene based two-dimensional nanomaterial.And the two-dimensional laminar nano-material has a large specific surface area and rich conjugate structures and functional groups of additional sites.There are many methods of dimensionality reduction and inserted layer and the function of modification to adjust and control the performance of the material so graphene based two-dimensional materials have been used widely in the field of anti-corrosion has good application prospect.Conductive polyaniline and its substituted derivatives are easy to be synthesized by chemistry or electrochemistry,have good environmental stability and different REDOX states,and can adjust their properties,so they are widely used in anticorrosive coatings.Conductive polyaniline and graphene oxide composites due to its excellent mechanical properties,electrorheological effect and the barrier performance have been applied in many fields.As a result of many factors such as low adhesion strength and compatibility of the individual elements of the polymer between graphene may not be strong,the application of fillers in improving anticorrosion performance were limitations.Polydopamine is a promising green material,which is non-toxic and biodegradable.Graphene oxide two-dimensional skeleton contains abundant oxygen-containing groups,which can react with the amine group of polydopamine.Therefore,polydopamine is expected to be used as molecular linkers to connect the graphene oxide nano-sheet to the surface of the metallic matrix,enhancing the adhesion of graphene oxide nano-sheet,and synthesized a dense and stable graphene oxide film.Nano-silica has excellent properties such as ultraviolet resistance,chemical resistance,as coating filler;it can improve the anti-aging performance and mechanical strength of the coating,and has been widely used in the fields of special coating,fireproof materials,industrial additives and building materials anti-corrosion.The composite and modification of two-dimensional layered GO nanomaterial,increasing the spatial structure of graphene oxide and enhancing its dispersion in the coating are feasible methods to improve the anti-corrosion performance of the coating.This paper innovatively modified and compounded GO with different nanomaterial,by adding these composite as an smart filler into the water-based coating,and explored the anti-corrosion mechanism of the modified water-based coating.The effects of different reaction conditions and ratio parameters on the morphology and properties of PANI-GO,PDA-PANI-GO and SiO2-PANI-GO nanocomposites were studied by orthogonal design,and the experimental parameters were optimized.Then the GO,PANI-GO,PDA-PANI-GO,SiO₂-PANI-GO were used as fillers by adding into the water-borne alkyd coatings.Using electrochemical impedance tests and dynamic polarization curve tests studied the anticorrosion mechanism of modified waterborne coating,at the same time,the mechanical properties of modification of waterborne coating,the adhesion of the base and the coating and hydrophobic properties of the coating.SEM,XRD,FT-IR and other materials characterization were conducted and the results show that the best preparation parameters of PANI-GO was reacting at room temperature for 18 hours,electrochemical impedance spectroscopy and dynamic polarization curves characterization results showed that best ratio of PDA and PANI-GO was 2:1.The anti-corrosion performance of PDA-PANI-GO modified waterborne alkyd varnish was improved;possible mechanism is due to the low surface tension of water-borne alkyd varnish,the coating prone to form micro defects shrinkage cracks in the process of solidification.In corrosive environments,corrosive substances can easily penetrate the coating through those micro-defects and then severely corrode the substrate.The structure of PDA-PANI-GO composite is nano-layer with uniform button shape,which can provide physical barrier effect and enhance the hydrophobicity of the coating surface,increasing the difficulty of the corrosive substances to contact the material and corroding materials.In addition,PANI-GO contains a large number of rigid structures and PDA is highly viscous,so the composite can fill the defects and cracks of pure water-based alkyd varnish.The ratio of SiO₂ to PANI-GO is 1:4;the SiO₂-PANI-GO modified waterborne alkyd varnish anticorrosion performance is greatly increased.The anticorrosive mechanism of the additives may due to structure of the composite which is the combination of layered GO,fibrous PANI and spherical SiO₂.The three-dimensional barrier structure of point,line and plane,can provide all-round physical barrier effect,increase the difficulty of the corrosive substances to contact the material and the path of the surface to the substrate.Based on the excellent properties of PANI-GO compound,nano-SiO₂ enhances the ultraviolet resistance and chemical resistance of the coating.