Exploration of Compatibility between Surface Pretreatment and Waterborne Epoxy Varnish Coating on Collaborative Anti-Corrosion for 2024 Aluminum Alloy

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