Investigating the corrosion inhibition of aluminium by diamine derivatives in hydrochloric acid: a multi-technique approach

The assessment of two diamine derivatives, TMD and IPDA, as corrosion inhibitors for aluminium in hydrochloric acid (HCl) at concentrations of 0.2 M, 0.3 M, and 0.4 M. (4S)—2,2,4-trimethyl hexane-1,6-diamine (TMD) and (1R,3R)-3-(amino methyl)-3,5,5-trimethyl cyclohexane-1-amine (IPDA) are verified for their ability to inhibit corrosion of Al in acidic conditions. The evaluation is conducted using electrochemical impedance spectroscopy (EIS), potentiodynamics polarization (PDP), and gravimetric methods. The inhibitors' effectiveness depends on their concentration (ranging from 20 to 50 mM) and molecular structure. Because TMD has more anchoring functional groups, it had the best inhibitory efficacy, reaching a maximum of 98.3% at 50 mM concentration. It is looked into how temperature (313–333 K) affects corrosion behaviour. As per Langmuir’s adsorption isotherm, the temperature probably influences the ability of inhibitors to adsorb on the surface of aluminium, pointing to a monolayer adsorption mechanism. Calculated and described are the thermodynamics activation factors for the dissolution process of Al in both inhibited along uninhibited solutions. The stability of the inhibitor-Al contact and the reaction kinetics are revealed by these characteristics. The creation of a protective covering on the Al surfaces was validated by surface investigation techniques such as atomic force microscopy, scanning electron microscopy, and energy-dispersive X-ray (EDX) analysis, demonstrating the inhibitors’ efficacy in preventing corrosion. The inhibitors’ molecular chemical makeup as well as the degree of inhibitory efficacy is correlated in theoretical investigations employing molecular dynamics simulations and density functional theory. Theoretical calculations shed additional light on the adsorption mechanism.