Preparation Of Zinc-aluminum Bimetallic Coating And Its Anti-corrosion Performance

In recent years,cold galvanizing coating has gradually replaced hot-dip galvanizing technology in the field of corrosion protection for steel structures due to its high corrosion resistance,convenient construction,high cost-effectiveness,and excellent overall performance.However,cold galvanizing still faces some problems that limit its development speed.The coating surface of cold galvanizing coating contains many pores,and the coating’s resistance to penetration is poor.Additionally,the high reactivity of zinc powder itself can react with corrosive media,and zinc powder that is not completely covered by resin is consumed before it can fully exhibit its cathodic protection function,which affects the effectiveness of cathodic protection.In this article,based on the research of cold galvanizing coating,we have developed cold galvanizing and cold aluminum composite coatings with high shielding effectiveness,zinc-aluminum alloy coatings,and water-based zinc-aluminum coatings to address the above issues.The research content and main conclusions are as follows:1.This article studied the effects of the types and amounts of film-forming resins,anti-settling agents,adhesion promoters,and leveling agents on the properties of cold galvanizing and cold aluminum coatings,the effect of the amount of aluminum-silver paste in cold aluminum coatings on the water absorption and electrochemical properties of the coating,and the effect of the thickness of cold galvanizing and cold aluminum coatings on the electrochemical properties of composite coatings.The results show that acrylic resin is more suitable as the film-forming material for cold galvanizing coatings,and the combination ratio of 0.3 ω%polyamide wax and 1.2 ω%bentonite has the best anti-settling effect.The polyester adhesion promoter LTW at a dosage of 0.8%can effectively improve the coating’s peel strength,flexibility,and impact resistance.Adding 0.15 ω%of organic modified polysiloxane leveling agent can effectively solve the problem of bubbles and pinholes in cold aluminum coatings.When the aluminum-silver paste is added at a ratio of 7 ω%,the water absorption of the cold aluminum coating is 1.7%,and the impedance value of the coating is the highest.According to the results of electrochemical analysis,the best combination for composite coatings is cold galvanizing 60 μm+cold aluminum 20μm.The results of salt spray test and corrosion potential test show that the composite coating can resist neutral salt spray for 4500h,which is in the cathodic protection time period of 4000h of the substrate.2.On the basis of the formulation research of cold-coated zinc coating,the effect of the dosage of spherical zinc powder and the ratio of flake aluminum powder and flake zinc powder in zinc-aluminum alloy powder on the corrosion resistance of zinc-aluminum coating was studied by orthogonal experimental methods,and the surface morphology and corrosion products before and after corrosion of cold-coated zinc coating were studied by SEM and XRD and other characterization methods.The results show that the mix ratio of anti-rust filler with the best salt spray resistance is spherical zinc powder:zinc in alloy:mass ratio of aluminum in alloy=25:22:13.The self-corrosion potential test results show that the cathodic protection time of zinc-aluminum coating for substrate is 3000h,and the cold zinc coating is 1500h,and the salt spray test results show that the salt spray resistance time of zinc-aluminum coating is 3500h,and the cold zinc coating is 2000h.The presence of flake zinc powder and flake aluminum powder before corrosion enhances the shielding and protection effect of zinc-aluminum coating,and the joint action of corrosion product flake aluminum powder and ZnAl2(OH)16CO3·4H2O enhances the shielding effect of zinc-aluminum coating.3.The study investigated the effects of waterborne film-forming resin types,polyurethane associative thickener,and waterborne polyurethane rheological additive,as well as hyperbranched polyester adhesion promoter on coating performance.Additionally,the study explored the influence of the waterborne aluminum silver paste amount in the resin solution on the salt spray resistance and electrochemical properties of the waterborne zinc aluminum coating.The results showed that the coating prepared using waterborne epoxy resin emulsion(AERS3260)as the film-forming material exhibited the best coating performance,with a volatile organic compound(VOC)emission of 98g/L,which meets the standard requirements.The optimal amount of anti-sedimentation agent was 0.4%U905+0.6 ω%BYK-420,and when the waterborne adhesion promoter AMORSO-482 was added at 0.6 ω%,the bonding strength between the coating and substrate reached a maximum of 6.1 MPa.When the waterborne aluminum silver paste amount was 3%,the waterborne zinc aluminum coating provided a cathodic protection time of 2500h for the steel substrate and a salt spray resistance time of 3000h.