Effect of adsorption of two green biopolymers on the corrosion of aluminum in 1.0 M NaCl solution: Physicochemical, spectroscopic, surface and quantum chemical exploration

Although aluminum is an extremely versatile material and can be manufactured and used for a wide range of industrial purposes, it has a limited resistance to corrosion. Hence, the efficacy of two linear biopolymers, keratan (Ker) and chitosan (Chi), was explored, for the first time, as ecologically safe metallic corrosion inhibitors (CIs) for Al in 1.0 M NaCl solution at different temperatures. For performing this study, several experimental and theoretical methods were applied. By combining these methods, it was confirmed that the investigated biopolymers were set to be effective inhibitors for Al corrosion in 1.0 M NaCl solution. Using a 500 mg/L dose of CIs, inhibition efficiencies (% IEs) of 92.7 % and 86.4 % were achieved for Ker and Chi, respectively, indicating their strong adsorption on the metal surface. Thermodynamic and kinetic investigations signified that the adsorption was founed to be physical and obeyed the Langmuir isotherm. The kinetics and mechanism of Al corrosion as well as its inhibition by the tested biopolymers were inspected. The results demonstrated that these biopolymers behaved as mixed-type and interface-type inhibitors. To investigate the inhibition mechanism, theoretical quantum chemical methods were also applied. The experimental investigations were validated by theoretical computations.