Electrochemical thermodynamic and kinetic studies of the behaviour of aluminium in hydrochloric acid containing various benzotriazole derivatives

In this study the inhibitive behaviour of benzotriazole, 5-methyl benzotriazole, 5-chloro benzotriazole and 5-nitro benzotriazole oil the corrosion of pure aluminum in 0.1 M HCl has been investigated by the potentiostatic polarisation technique. For this purpose, corrosion potentials E-corr, corrosion rates i(corr), anodic and cathodic Tafel slopes beta(a), beta(c), inhibition efficiencies IE, and surface coverages theta, were determined in 0.1 M HCl solutions containing various concentrations (i.e. 1 x 10(-5) M, 5 x 10(-5) M, 1 x 10(-4) M, 5 x 10(-4) M, 1 x 10(-3) M) of benzotriazole derivatives. The efficiency of the studied benzotriazole derivatives at a efficiency of the strudied benzotriazole derivatives at a concentration of 1 x 10(-4) M was found be in the following order: 5-nitrobeinzotrizole > 5-methyl benzotriazole > 5-chloro benzotriazole > benzotriazole. It was observed that the benzotriazole derivatives were behaving as cathodic inhibitors and the inhibiting action of these heterocyclic compounds was mainly due to adsorption on the metal surface, which parallels the total negative charge of each molecule. Front the adsorption isotherms, values of the free energy of adsorption DeltaG(ads) and the equilibrium constant K-ads for the adsorption processes were calculated Corrosion rates were determined electrochemically, at 20degreesC, 30degreesC, 40degreesC, 50degreesC and 60degreesC with 1 x 10(-4) M or 1 x 10(-3) M of these compounds in 0.1 M HCL From the corrosion rates obtained at different temperatures, activation parameters for the corrosion processes such as activation energies E-a, activation enthalpies DeltaH* and activation entropies DeltaS* were determined and possible mechanisms for the corrosion and inhibition processes have been proposed.