Cailiao Baohu (Nov 2023)
Exploration of Compatibility between Surface Pretreatment and Waterborne Epoxy Varnish Coating on Collaborative Anti-Corrosion for 2024 Aluminum Alloy
Abstract
In order to reveal the effects of phosphating, anodizing, and silanizing pretreatments on the anti-corrosion performance of the entire coating system prior to applying waterborne epoxy varnish to the aluminum alloy (AA) surface, three kinds of pretreatments of zinc phosphating, electrochemical anodizing, and epoxide silanizing were carried out on the surface of 2024 AA. Each pretreated surface was subsequently coated with waterborne epoxy varnish. Characterization methods such as scanning electron microscopy (SEM), X-ray diffraction (XRD), adhesion tester, X-ray photoelectron spectroscopy (XPS), and electrochemical workstation were used to characterize the microstructure, phase composition, adhesion, chemical composition and electrochemical impedance spectroscopy of three systems. The effects of three surface pretreatments on the anti-corrosion effect of waterborne epoxy varnish coatings on aluminum alloy substrates were compared. The compatibility of the synergistic anticorrosive effect of three pretreatment and waterborne epoxy varnish coatings on aluminum alloy surfaces was explored. Results indicated that all three pretreatments could improve the anti-corrosion effect of waterborne epoxy varnish coatings on aluminum alloy substrates. The performance order of compatibility of the synergistic anti-corrosion effect between pretreatment and coating was epoxy based silylation>electrochemical anodic oxidation>zinc based phosphating. The compatibility of synergistic anti-corrosion effects of three pretreatments combined with a waterborne epoxy varnish coating were closely related to the microstructures, chemical compositions of the phosphate film, anodic oxide film and silane film, as well as their interfacial bonding forms with the aluminum alloy substrate.
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