Invasive weed of Mikania micrantha extract as a novel efficient inhibitor for the corrosion of aluminum in HNO3 solution

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The inhibition effect of Mikania micrantha extract (MME) on 1060 aluminum corrosion in 0.10 M HNO3 was investigated by both experimental and theoretical methods. The results demonstrate that MME performs excellent inhibition with the maximum inhibition efficiency of 97.6% at 0.50 g L-1. The adsorption of MME on aluminum surface obeys Langmuir, Freundlich, Temkin, El-Awady thermodynamic-dynamics, Flory-Huggins isotherm, and it is a mixed-type inhibitor. Nyquist consists of a capacitive loop at high frequency, an inductive loop at medium frequency, and a small capacitive section at low frequency. The impedance of EIS is gradually enhanced along with the increase of MME concentration. SEM and AFM images confirm that MME can efficiently retard the metallic corrosion. XPS demonstrates that the adsorptive inhibition film is composed of polar functional groups containing C and O elements of CO, C─OH/C─O─C, C─H/C─C from MME. LC-MS illustrates that MME contains multiple active ingredients of quercetin, caffeic acid, vanillin and guanine. The anti-corrosion effect of MME is mainly attributed to the synergistic effect of multi-components. Quantum chemical calculations and MD simulations indicate that the presence of multiple active sites in quercetin, caffeic acid, vanillin and guanine, including benzene/heterocyclic and carboxyl groups, facilitates their interaction with aluminum surface.