Smart‐Release Ion‐Exchanged Ca‐Montmorillonite for Corrosion Protection of AA2024 Aluminium Alloy

This study reports the development of smart‐release anti‐corrosion pigments based on ion‐exchanged montmorillonite (MMT) for the protection of high‐strength AA2024 aluminium alloy. Zn 2+ ‐ and Mn 2+ ‐modified MMTs were synthesized by liquid‐phase ion exchange. XRD and SEM/EDX confirmed the preservation of the montmorillonite structure and incorporation of the modifying cations. The inhibiting performance of the pigments was evaluated in acid rain using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and gravimetric measurements. Zn‐modified MMT provided the highest protection, reducing the corrosion current density from 1.2 × 10 −6 to 7.9 × 10 −8 A cm −2 after 168 h and achieving inhibition efficiencies of 93.4%, 93.7%, and 91.8% by polarization, EIS, and gravimetric measurements, respectively. Mn‐modified MMT showed lower inhibition efficiency (47%–54%), whereas Zn–Mn‐modified systems provided intermediate protection (75%–90%). The superior performance of Zn‐MMT may be associated with the release of Zn 2 + cations from montmorillonite interlayers and their possible interaction with OH − ions generated during cathodic oxygen reduction. These processes may favor the formation of sparingly soluble zinc‐containing species, potentially including Zn(OH) 2 , which could contribute to the development of a protective surface layer and reduce the electrochemically active area. Zn‐modified MMT therefore shows strong potential as an environmentally safe inhibiting pigment for anti‐corrosion coatings.