Unraveling the enhanced interfacial adhesion of epoxy coatings on cerium conversion-coated metals: a multiscale investigation by thermodynamic and molecular dynamics

Purpose The interfacial performance of epoxy coatings strongly influences their long-term corrosion protection on metallic substrates. This study aims to elucidate how cerium-based conversion coatings affect epoxy/metal interfacial interactions and adhesion mechanisms. Design/methodology/approach Electrochemical impedance spectroscopy (EIS) and pull-off tests were used to assess interfacial stability and adhesion on differently pretreated substrates. A surface-energy-based thermodynamic model was implemented to predict interfacial bonding strength. In addition, density functional theory (DFT) calculations and molecular dynamics (MD) simulations were conducted to probe atomic-scale interactions and dynamic adsorption behavior at the epoxy/CeO2 interface. Findings Cerium conversion coated substrates exhibited superior interfacial stability and adhesion compared to other pretreatments, as indicated by higher impedance values and cohesive failure within the coating. Thermodynamic predictions of interfacial bonding strength were consistent with EIS and adhesion results. DFT results revealed enhanced electronic interactions and charge transfer at the epoxy/CeO2 interface, while MD simulations demonstrated stable adsorption and resistance to interfacial disruption under realistic conditions. Originality/value This work integrates experimental electrochemical and adhesion characterization with thermodynamic and atomistic simulations to provide a predictive understanding of corrosion-resistant coating interfaces, offering a rational basis for interface design beyond conventional trial-and-error approaches.