Study on the corrosion resistance of sulfonated graphene/aluminum phosphate composites in waterborne polyurethane coatings

Abstract

Abstract Sulfonated graphene/aluminum phosphate (SG/AlPO4) composites were synthesized by precipitation method, and composites with different mass ratios were added to water-based polyurethane (WPU) resins to prepare coatings. According to tests, composites with the addition of 2 wt% composite coating has good anticorrosion performance, and its protection efficiency is increased by 79.6% compared with pure resin. In the early stage of the corrosion, the SG layer forms the barrier. During the corrosion process, the SG layer was destroyed, the phosphate ions decomposed by the exposed spherical AlPO4 in the corrosive medium and the divalent iron ions on the iron-based surface form a stable precipitation protective layer to achieve the anticorrosion effect. From the EIS test, the coating with 2 wt% composite material has a larger radius of curvature in the Nyquist diagram at different time periods. According to the fitted circuit, it is further confirmed that the precipitation protection layer has a larger resistance value. After soaking for 24 h the resistance value is the largest, which is 1.231 × 104 Ω cm2.