Influence of the sol-gel mesoporosity on the corrosion protection given by an epoxy primer applied on aluminum alloy 2024-T3

Silica-based sol-gel mesoporous thin films were applied on aluminum 2024 as first pretreatment surface whereas an epoxy coating was applied as top layer. Non porous and mesoporous sol-gel films were synthetized via EISA process using Pluronic P123 and F108 as templating agents. Two different kinds of alkoxy-silane mixture were compared using inorganic or hybrid precursors. The morphology, the pore size distribution of sol-gel thin films were observed by TEM, FE-SEM and measured by a quartz crystal microbalance (QCM). The anticorrosion performance and characteristics of sol-gel films were assessed by EIS measurements. The compatibility between sol-gel film and epoxy coating was studied by salt spray test and swelling in N-methylpyrrolidone. The goal of this study is to highlight the role of pretreatment porosity at the sol-gel film/organic coating interface on aluminum 2024 substrate. The higher pore size distribution of the hybrid sol-gel formulation promotes adhesion and anticorrosion performance at aluminum 2024 substrate/sol-gel film/epoxy coating interface.