In Situ-Grown LDH Coatings Intercalated with Organic Inhibitors on AA2024 Aluminum Alloy: Synergistic Corrosion Inhibition and DFT-Based Insights

In this study, ZnAl layered double hydroxide (LDH) nanocontainers were grown in situ on AA2024 aluminum alloy through a controlled hydrothermal process, using the native oxide layer as an internal aluminum source, and succinic acid (SA) and tartaric acid (TA) inhibitor anions were subsequently intercalated into the LDH interlayers via an optimized ion-exchange treatment performed at 60 °C under ambient pressure, with exposure times from 15 min to 5 h to evaluate the effect of intercalation duration on inhibitor uptake and film stability. Structural and morphological analyses by X-ray diffraction (XRD) and scanning electron microscopy (SEM) confirmed the formation of well-crystallized LDH films and the successful incorporation of the organic inhibitors. Corrosion resistance in 3.5% NaCl, assessed through immersion tests, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PDP), showed that the SA-intercalated coating achieved an inhibition efficiency of 95.1% after 48 h, significantly higher than the 62.5% obtained for the TA-based coating, while the pristine LDH layer provided only short-term barrier protection. The superior performance of LDH_SA is attributed to the synergistic effects of chloride ion trapping within the LDH matrix, the formation of a hydrophobic protective layer generated by released SA, and a self-healing response driven by ion-exchange mechanisms. Density functional theory (DFT) and Monte Carlo (MC) simulations further revealed strong physisorption and chemisorption interactions between the inhibitors and both the LDH surface and the aluminum substrate, and the combined experimental-theoretical results demonstrate that LDH_SA constitutes a robust, environmentally friendly, and highly efficient corrosion-mitigation coating for aluminum alloys in chloride-rich environments.