Enhanced Corrosion Resistance of Water-Based Aluminum Phosphate Coatings via Graphene Oxide Modification: Mechanisms and Long-Term Performance

In this study, we have developed a water-based aluminum phosphate (WAP) coating consisting of a base layer and a surface layer. Graphene oxide (GO) was used to modify the base layer. Three different GO concentrations—0.5, 0.75, and 1 wt.%—were employed to assess their impact on the corrosion resistance of the coating and to explore the underlying mechanisms. The corrosion resistance mechanism was also examined. In the coating, GO combined with phosphate to form large blocks that effectively blocked the pores, and the porosity decreased with the increase in GO content. This led to an improvement in the substrate protection efficiency by over 10%. Impedance spectroscopy revealed that the main mechanism behind the enhanced corrosion resistance was the shielding effect of GO, which created a “maze effect” that improved the coating’s protective properties. However, an excessive amount of GO reduced the corrosion resistance of the coating. Overall, the WAP coating modified with 0.75 wt.% GO exhibited the best corrosion resistance.