Self-assembled NAnophase Particle (SNAP) surface treatments for corrosion protection of AA2024-T3

Abstract

The Self-assembled NAnophase Particle (SNAP) process is a method of forming functionalized silica nanoparticles in situ in an aqueous-based sol–gel process, and then crosslinking the nanoparticles to form a thin film. Using the SNAP approach, coating components and materials can be designed and built up from the molecular level, in a sort of “bottom-up” design process. The SNAP surface treatment coatings have been investigated in a 2000 h salt spray test with a chromated primer and topcoat as a potential surface treatment replacement for the current chromate-based approach. Based on these results, paint systems incorporating the SNAP surface treatment with a chromated primer exhibited equivalent corrosion protection when used with a fully chromated system. The formulation of the SNAP surface treatment coatings used in this study did not include a corrosion inhibitor(s). The SNAP coatings were not only chromate-free, but they contained no heavy metals and were water-based. In addition, these SNAP surface treatment coatings were also found to be effective when used in an appliqué topcoat system without a chromated primer, showing no film undercutting around the area of the scribe. Other possible formulations that could be developed using potent corrosion inhibitors in the SNAP process will also be presented.