Copper corrosion behaviour in the presence of binary system containing 5-methyl-1H-benzotriazole and gelatine as well as 1H-benzotriazole and gelatine in 0.01 mol dm(-3) H2SO4 with the addition of different concentration of Cl-ions was investigated in this study. The corrosion inhibition effect of these compounds was examined by electrochemical techniques (open circuit potential, potentiodynamic polarization and cyclic voltammetry measurements) and weight loss measurements. The surface analysis by scanning electron microscopy with energy X-ray spectroscopy was also performed to assess the morphology of untreated and treated surface of copper coupons. According to the potentiodynamic polarization results, these inhibitors showed good performance in the presence of Cl-ions and they act as mixed-type inhibitors. The inhibition efficiency of binary system is over 90% indicating that these compounds provide good copper protection in sulphate-chloride solutions. The results obtained from weight loss measurements are in good agreement with the results obtained by electrochemical measurements.