Corrosion inhibition of copper in 3 per cent NaCl solution by new bipyrazolic derivatives

The inhibition of the copper corrosion in aerated 3 per cent sodium chloride solution was studied by using electrochemical polarisation, weight loss and impedance measurements in the presence of different concentration of synthesised bipyrazolic compounds: N,N-bis (3,5-dimethylpyrazol-1-ylmethyl) butylamine (bipy1); N,N-bis (3,5-dimethylpyrazol-1-ylmethyl) allylamine (bipy2); N,N-bis (3,5-dimethylpyrazol-1-ylmethyl) ethanolamine. (bipy3); N,N-bis (3,5-dimethylpyrazol-1-ylmethyl) cyclohexylamine (bipy4); N,N-bis (3-carbomethoxy5-methylpyrazol-1-ylmethyl) cyclohexylamine (bipy5); N,N-bis(3-carboethoxy-5-methylpyrazol-1-ylmethyl) cyclohexylamine (bipy6). The inhibition efficiencies obtained from cathodic Tafel plots, polarisation resistance and weight loss are in good agreement with electrochemical impedance spectroscopy (E15) measurements. All these additives were found to be excellent inhibitors of copper corrosion. The difference in inhibition efficiencies of these inhibitors was not big, but the optimum concentration for maximum efficiency was slightly dependent on the substitution of each molecule. The studied molecules act as mixed-type inhibitors. Detailed study of bipyl shows that the maximum inhibition efficiency revolves around 99 per cent from 5 x 10(-4) M of inhibitor. This latter adsorbs on the copper surface according to the Frumkin isotherm model. The inhibition efficiency of bipyl decreases with the rise of temperature in the range 25 - 60 degreesC.