Mechanistic origins of corrosion protection of aluminum alloys by graphene/polyetherimide nanocomposite coatings

Abstract Light-weighting vehicular components through adoption of light-metal structural alloys holds promise for reducing the fuel consumption internal combustion engine vehicles and increasing range battery electric vehicles. However, alloyed microstructure surface precipitates aluminum render these materials susceptible to corrosion under modest excursions from neutral pH. Traditional chromium-based anodic passivation layers are subject increasingly stringent environmental regulations, whereas options sacrificial cathodic films sparse electropositive metals. While hybrid nanocomposite coatings have shown initial promise, mechanistic underpinnings remain poorly understood. Here, a fully imidized polyetherimide (PEI) resin is utilized as continuous phase with inclusion unfunctionalized exfoliated graphite (UFG). A comprehensive investigation mechanisms protection reveals key fundamental design principles underpinning inhibition. First, strong interfacial adhesion, which PEI facilitated by binding imide carbonyl moieties Lewis acidic sites on Al surfaces. Second, miscibility ion-impervious nanoscopic UFG fillers stabilization substantial interphase region at UFG/PEI boundaries that result in minimizing free volume filler/polymer interface. Finally, extended tortuosity ion diffusion pathways imbued below-percolation-threshold 2D fillers. These three help govern modulate transport electrolyte/coating interfaces coating/metal interface crucial preservation barrier properties. The results suggest an approach systematically activate multiple modes inhibition rational across hard-to-abate sectors where light metal likely play prominent role.