Kinetics and thermodynamics of aluminium dissolution in 1.0 M sulphuric acid containing chloride ions

The dissolution of aluminium in 1 M sulphuric acid solutions containing different chloride ion concentrations (0.01–0.06 M) were studied at 25, 30, 35 and 40 °C using electrochemical impedance spectroscopy (EIS) technique and polarization curves measurements. The kinetic rate equation, under the experimental condition described, was derived and found to verify the following relationship:V=kobsK2CCl−n1+K2CCl−nwhere V is the corrosion rate, kobs and K2 are the dissolution rate constant of aluminium oxide–chloride complex and the equilibrium constant of chloride ions adsorbed at aluminium oxide surface, respectively. The kinetic and thermodynamic energy parameters were calculated and their values indicate that chloride ions are chemisorbed onto the aluminium oxide surface and the formation of oxide–chloride complex is the rate-determining step.