The inhibition of copper corrosion in 0.1 m NaCl under heat exchange conditions

The inhibiting effects of 5-methylbenzotriazole, 5-chlorobenzotriazole, 5-n-hexylbenzotriazole, 2,4-dimercaptopyrimidine and 2-amino-5-mercaptothiadiazole at 0.1 and 0.5 mM concentrations on the copper corrosion in 0.1 M NaCl solutions under heat exchange conditions (Delta T = 60 degrees C) are examined. The inhibiting efficiency of the different additives is evaluated from anodic and cathodic polarization curves and from the polarization resistance values after 2 h. The variation of the corrosion rate of copper with time is followed through the measurement of the polarization resistance values for a period of 100 h. The influence of the inhibitors is evaluated by the changes of the polarization resistance values with time. All the tested inhibitors at 0.5 mM concentration show high inhibiting efficiency. Only at 0.1 mM concentration, an appreciable decrease of the inhibiting efficiency of the thiadiazole derivative is observed. The examined compounds can afford protection to an already corroded copper surface, blocking or at least reducing significantly the corrosion process. In all experimental conditions investigated 5-n-hexylbenzotriazole provides the best inhibition efficiency.