Corrosion initiation and propagation in Cu–Al laminated composites: Roles of interfacial IMCs (Al2Cu, AlCu, Al4Cu9) and microgalvanic effects

Novel copper-aluminum laminated composites, boasting advantages like light weight, high strength, excellent electrical/thermal conductivity, and low cost, are now widely used in shipbuilding, electronics, metallurgy, aerospace, and daily life. However, in corrosive environments, large electrochemical potential differences between copper and aluminum trigger severe interfacial galvanic corrosion in these composites, impairing their long-term performance. Utilizing first-principles calculations, this study systematically investigates the thermodynamic and electronic properties of the three primary interfacial intermetallic compounds (Al 2 Cu, AlCu, Al 4 Cu 9 ), calculates the surface energies and work functions of three low-index surfaces ((100), (110), (111)), and analyzes the adsorption performance of Cl - at six sites on Al 2 Cu(100). The results indicate that the composite's corrosion is not solely due to macro-galvanic Cu/Al effects but also involves multi-level micro-galvanic corrosion facilitated by interfacial intermetallic compounds. The driving force behind this corrosion is the work function gradients between these intermetallic compounds. Potential differences lead to directional electron migration along the path Al→Al 2 Cu→AlCu→Al 4 Cu 9 →Cu, establishing a self-sustaining electrical current. The adsorption of Cl - on Al 2 Cu(100) induces a microcell effect through electron defects and complex exchange, creating localized potential differences that accelerate the spread of corrosion and the dissolution of Al. These findings offer atomic-scale insights into interfacial mechanisms and provide valuable insights that could serve as a reference for designing corrosion-resistant Cu-Al laminated composites. • Reveals that the deterioration of Cu-Al laminated composites originates from multilevel micro-galvanic couples facilitated by interfacial intermetallic compounds (IMCs) (such as Al 2 Cu, AlCu, and Al 4 Cu 9 , rather than solely from macro-scale Cu/Al galvanic effects. • Demonstrates that work function gradients across IMCs are the primary cause of corrosion, establishing a directional electron migration path (Al→Al 2 Cu→AlCu→Al 4 Cu 9 →Cu) that maintains a self-sustaining current. • Shows that Cl - adsorption on Al 2 Cu(100) induces localized microcell effects through charge redistribution, creating significant potential differences that accelerate Al dissolution and corrosion propagation. • Provides actionable strategies for enhancing corrosion resistance in Cu-Al composite laminates (CLMs): (1) adjusting the electronic structure/distribution of IMCs to minimize work function gradients; (2) employing surface coatings/inhibitors to prevent Cl - adsorption and disrupt microcells.