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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‐carbomethoxy‐5‐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 (EIS) 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 bipy1 shows that the maximum inhibition efficiency revolves around 99 per cent from 5×10⁻⁴ M of inhibitor. This latter adsorbs on the copper surface according to the Frumkin isotherm model. The inhibition efficiency of bipy1 decreases with the rise of temperature in the range 25 – 60°C.

It does not need much imagination to picture fairly vividly the immense problems occurring in industry due to the ravages of corrosion. Water is a universal service, but by reason of the impurities • it contains in its natural state it may rapidly corrode the heating system or the cooling system or the process system in which it is employed. The photographs in the following article show examples of what may happen.

Corrosion inhibitors are widely used in industry, although in many cases their surface chemistry is not well understood. Several nitrogen‐containing organic compounds have been used as corrosion inhibitors. Corrosion inhibition is a surface process which involves the specific adsorption of inhibitors on the metal surface. The extent of inhibition of metallic corrosion may depend on the nature of the metal surface and extent of adsorption of the inhibitor. The type of interaction of the inhibitor on the metal surface during corrosion has been deduced from its adsorption characteristics.

Zinc is one of the most important nonferrous metals and finds extensive use in metallic coatings. It is resistant to atmospheric attack and corrodes rapidly only in highly polluted air. It is resistant to most fresh waters but its resistance to sea water and to very soft water is lower. In many aerated hot waters, reversal of polarity between zinc and iron occurs at temperatures of 60°C or above. The corrosion products of zinc are readily soluble both in alkalis and acids and protect the metal surface only in neutral media. In neutral solutions, zinc is corroded mainly by oxygen depolarisation. The dissolution rate of zinc in acids is greatly affected by the over‐potential of hydrogen evolution at cathodic inclusions.