Abstract
The corrosion behavior of unalloyed copper (99.999% Cu) in freely aerated hydrochloric acid pickling, 0.50 M HCl, solutions and its inhibition by different concentrations of 3-amino-1,2,4-triazole (ATA) and 3-amino-5-mercapto-1,2,4-triazole (AMTA) were reported. The experiments have been carried out using weight-loss, potentiodynamic polarization (PDP), chronoamperometry (CA), electrochemical impedance spectroscopy (EIS), and Raman spectroscopy investigations. Weight-loss data indicated that copper dissolves rapidly in HCl solution due to the increased weight loss with increasing the exposure period. The addition of ATA and AMTA molecules to the acid solution remarkably decreased both the weight-loss and corrosion rate for copper; further decreases were obtained with the increase of these compounds concentrations due to the increase of their inhibition efficiencies. PDP, CA, and EIS measurements showed clearly that the presence of ATA and AMTA and the increase of their concentrations significantly decrease the corrosion reactions for copper in HCl solutions. The detection of ATA and AMTA molecules on the copper surface by Raman spectroscopy confirmed that the inhibition of copper corrosion in the acid solution is achieved by strong adsorption of these organic molecules onto the copper surface preventing the formation of cuprous chloride and oxy-chloride complex compounds.