Abstract

The inhibition of copper corrosion in aerated 0.1 mol l-1 hydrochloric acid solutions was studied using electrochemical polarization in the presence of different concentrations of benzotriazole and its two derivatives, 5-chloro and 5-methyl benzotriazole. The inhibition efficiencies obtained from cathodic Tafel plots increased markedly with increase in the additive concentration. Benzotriazole and 5-methyl-benzotriazole were found to be cathodic type corrosion inhibitors for concentrations higher than 10 -4 mol l-1 . However, the 5-chloro-benzotriazole was found to be a mixed inhibitor for concentrations up to 10-3 mol l -1, above this concentration the inhibitor behaves as an anodic type inhibitor. The inhibitors are physisorbed on the copper surface following a Langmuir's isotherm. The inhibition efficiencies depended on the inhibitor concentration and follows the order 5-chloro-benzotriazole > 5-methyl-benzotriazole > 1-H-benzotriazole. From the theoretical calculations, the change in the inhibition mechanism observed for 5-chloro-benzotriazole at concentrations higher than 10-3 mol l -1 is associated with the electronic acceptor characteristic of chloro, which increases the benzotriazole acidity allowing the formation of CuBTA.