Tetrazole derivatives as corrosion inhibitors for copper in chloride solutions

The inhibiting action of some tetrazole derivatives on the copper corrosion in chloride solutions has been studied. Experiments have been carried on OFHC copper in 0.1 M NaCl solutions with the following tetrazole derivatives at the 10(-3) M concentration: tetrazole (T), 5-mercapto-1-methyl-tetrazole (SMc-1Me-T), 5-mercapto(Na salt)-1-methyl-tetrazole (5NaMc-1Me-T), 5-mercapto-1-acetic acid(Na salt)-tetrazole (5Mc-1Ac-T), 5-mercapto-1-phenyl-tetrazole (5Mc-1Ph-T), 5-phenyl-tetrazole (5Ph-T) and 5-amino-tetrazole (5NH(2)-T) in the range of pH from 4 to 8 and at temperatures of 40 and 80 degrees C. Some inhibitors have been studied from 10(-5) to 6 x 10(-3) M. Cathodic and anodic polarisation curves were recorded after 1 h of immersion. Polarisation resistances measurements have been made as a function of the time in the 300 h experiment. The weight loss measurements have confirmed the electrochemical trend. The prefilming action of some tetrazole derivatives has been evaluated. The interaction between the organic molecules and the metal surface has been studied by means of FTIR reflection spectra. All the inhibitors, except the 5Mc-1Ac-T which stimulates the corrosion, show an inhibiting efficiency from 50 to 99%. In every case the inhibiting efficiency increases with increasing pH value. 5Mc-1Ph-T and 5Ph-T show the better protective characteristics. Copyright (C) 1996 Elsevier Science Ltd