Abstract
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•The epoxy coating on Al alloys was tested in 3 wt% NaCl solution using a salt spray test chamber.•The anticorrosive behavior of the Al alloys was monitored by EIS measurements and theoretical studies.•The lessening of impedance with submersion time means that the electrolyte scatters into the epoxy coating.•DFT calculations were used to determine the coatings adsorption centers.•The MC and MD calculations support the coating's strong adsorption interaction with the metal surface.
In this work, a formulation based on epoxy coating composed of DGEBA cured with polyaminoamide has been used as anti-corrosive material for aluminum alloys (2024-T3, 5086 and 7075-T6) substrates for accelerated corrosion assays. The epoxy coating on aluminum alloys samples was tested in 3.0 wt% NaCl solution using salt spray test chamber. The anticorrosive behavior of the aluminum alloys samples under these conditions was monitored by impedance diagrams Bode and Nyquist plots and theoretical studies by DFT, MC and MD. The results showed that the evolution of the impedance modulus plots |Z|0.01 Hz values of the epoxy coating applied on AA2024-T3, AA5086 and 7075-T6 samples began from 2.63, 1.46 and 0.43 MΩ.cm2 after 1 h of immersion and finally reached 0.27, 0.26 and 0.24 MΩ.cm2 after 4392 h of immersion, respectively. The lessening of impedance with submersion time means that the electrolyte scatters into the epoxy coating and diminishes the boundary properties of the film. DFT calculations were used to determine the coatings adsorption centers. Additionally, the Monte Carlo and Molecular Dynamics calculations support the coatings strong adsorption interaction with the metal surface, providing molecular evidence for the epoxy molecule's adsorption behavior (geometry) and adsorption energy on the aluminum surface. Theoretical results (DFT, MC, and MD) corroborate the experimental results.