Experimental and computational exploration of the corrosion inhibition potential of Prunus cerasus leaves aqueous extract on D16T aluminum alloy in 3.0% NaCl solution

The present study examines the corrosion-inhibiting performance of Prunus cerasus leaves aqueous extract (PCLAE) for the protection of D16T aluminum alloy in a 3.0% NaCl medium. A comprehensive assessment was carried out using gravimetric analysis, electrochemical techniques - including potentiodynamic polarization and chronoamperometric measurements - and surface characterization, complemented by theoretical modeling. The results demonstrate that PCLAE provides significant corrosion mitigation, with inhibition efficiency increasing with both concentration and temperature. At an optimal concentration of 2.0 g·dm −3 , the extract achieved a maximum inhibition efficiency of 91.19% at 333 K. Electrochemical tests confirmed that PCLAE functions as a mixed-type inhibitor with a more pronounced effect on the cathodic reaction. At maximal inhibitor concentration the corrosion current density ( j corr ) decreased from 1.78·10 −4 A·cm −2 in the blank solution to 2.62·10 −5 A·cm −2 , corresponding to an efficiency of 85.27%. The adsorption process was confirmed to be spontaneous, as evidenced by the negative values of the standard Gibbs free energy of adsorption (up to −18.16 kJ·mol −1 ), and endothermic in nature, as indicated by the positive standard enthalpy of adsorption (ΔH 0 ads ) of 16.49 kJ·mol −1 . The obeying of adsorption to the Langmuir and Frumkin models, suggesting the formation of a monolayer stabilized by slight lateral attractive interactions between adsorbed molecules. The Density Functional Theory (DFT) calculations at the B3LYP/6–311G(d,p) level of theory identified polyphenols and low-molecular-weight organic acids as the most active components of the extract, attributed to their ability to efficiently transfer electrons to the Al(111) surface, facilitated by the presence of oxygen-containing functional groups and aromatic systems. Molecular Dynamics (MD) simulations revealed strong binding energies for key components like gallic acid (-613.41 kcal·mol −1 ) and L -phenylalanine (-577.31 kcal·mol −1 ) on the Al(111) surface in an aqueous phase, highlighting the crucial role of oxygen- and nitrogen-containing functional groups in forming a stable protective film. The strong correlation between experimental findings and theoretical modeling highlights the potential of PCLAE as an environmentally friendly and effective corrosion inhibitor for aluminum alloys exposed to chloride-induced degradation. • PCLAE adsorption forms a Langmuir–Frumkin monolayer; multilayer adsorption at low temperature. • Maximum inhibition efficiency of 91.19% is achieved at 2.0 g·dm −3 . • The inhibitor blocks active sites without altering the corrosion mechanism. • Planarity, aromaticity and electronegative atoms govern inhibition efficiency. • Mixed-type inhibition occurs via spontaneous physisorption.