| Corrosion is one of the most important factors threatening the safety of metal materials.Large-scale equipment production accidents caused by metal corrosion in production activities will directly endanger the safety of human life and property.Therefore,it is of great significance to study metal anti-corrosion coatings.The mainstream solvent-based epoxy anti-corrosion coatings contain a large amount of volatile organic compounds(VOC),which is inconsistent with people's safety,environmental protection and health concepts,so it is imperative to develop water-based epoxy coatings with excellent performance.At present,the performance of waterborne epoxy coatings still needs to be improved,and the good physicochemical properties of graphene materials have opened up a new research path for improving the performance of waterborne epoxy coatings.In this paper,the optimized formulation of waterborne epoxy resin coating was designed according to the optimized ratio of pigment and filler.The test proved the good performance of the optimized formulation.Based on the optimized formulation,graphene and graphene oxide were added to study the corrosion resistance and corrosion prevention mechanism of two graphene materials in waterborne epoxy resin coatings.The optimum ratios of six kinds of pigments and fillers for waterborne epoxy resin coatings were obtained by orthogonal test: m(iron red):m(talc):m(barium sulfate):m(zinc phosphate):m(wollastonite):m(mica powder)=7:2:2:2.5:2:1,and the pigment volume concentration(PVC)is 30.14%.From this optimization ratio,an optimized formulation of waterborne epoxy coating was designed.The coating prepared by the optimized formula has good basic properties.The coating has a neutral salt spray resistance of 2636 h,acid resistance of 150 h and alkali resistance of 68 d.Graphene/graphene oxide was used as a filler to study their effects on the corrosion resistance of waterborne epoxy resin coatings.The results show that with the increase of graphene/graphene oxide addition,the corrosion resistance of the coating increases first and then decreases.When the corrosion resistance of the coating is optimal: the amount of graphene added is 1.5%,at this time,the coating has acid resistance of 216 h,alkali resistance of 68 d,neutral salt spray resistance of 3500 h;And graphene oxide addition of 0.4%,at this time,the coating was resistant to acid for 228 h,alkali resistance for 98 d,and neutral salt spray for 3,720 h.The anti-corrosion mechanism of graphene/graphene oxide in waterborne epoxy resin coatings was further studied by scanning electron microscopy,coating contact angle measurement and coating electrochemical performance test,etc.From the test and analysis results,it is concluded that the addition amount of graphene/graphene oxide can be uniformly distributed in the coating when the addition amount is 1.5% and 0.3%~ 0.4%,respectively,which can effectively improve the compactness of the coating.The graphene material is distributed in a lamellar layer to form a “maze effect”;the addition of graphene/graphene oxide can increase the interface contact angle between the surface of the coating and the aqueous solution.The larger the amount of addition,the larger the contact angle;As the addition of graphene/graphene oxide increases,the coating self-corrosion potential and coating resistance increase first and then decrease,and the self-corrosion current density decreases first and then increases.The variation law of the equivalent circuit fitting parameters and the corrosion resistance of the corresponding coatings are consistent;The anti-corrosion mechanism of graphene in the coating can be divided into three stages:(1)forming a hydrophobic effect on the surface of the coating.(2)Forming a coating "maze effect".(3)High conductivity acceleration effect;Graphene oxide can participate in resin curing and improve the stability of resin molecules in corrosive media,which is one of the factors to improve the corrosion resistance of the coating.Graphene oxide does not significantly promote the negative effects of metal corrosion. |
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