Natural polycitric acid-curcumin for highly efficient corrosion inhibition of aluminum alloys

A new inhibitor called poly(citric acid-curcumin) (Cur-PCA) was synthesized to mitigate the corrosion of aluminum alloy heat exchange tubes in a low-temperature multi-effect seawater desalination plant. The corrosion-inhibiting properties of Cur-PCA on 3105 aluminum alloy were studied in a pickling solution of 1 mol/L HCl prepared using a 3.5 % NaCl solution at 25 °C. The investigation utilized weight loss analysis, electrochemical techniques, scanning electron microscopy (SEM), molecular dynamics simulation, and quantum chemical calculations. The findings demonstrated that Cur-PCA acted as a mixed-type inhibitor, predominantly inhibiting the cathodic reaction. At a concentration of 500 ppm, Cur-PCA exhibited an inhibition efficiency of 94.19 %. The adsorption behavior of Cur-PCA conformed to the El-Awady model, and it could spontaneously adsorb onto the surface of the aluminum alloy. Molecular dynamics simulation and quantum chemical calculations confirmed the spontaneous adsorption of Cur-PCA molecules on the aluminum alloy surface and explored the relationship between the structure of Cur-PCA and its corrosion inhibition effect.