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PurposeTo correlate the inhibitory effect of triazole compounds on the corrosion of copper in HCl at various temperatures by semi‐empirical molecular orbital theory.Design/methodology/approachTwo triazoles were selected as the best inhibitors among the triazole compounds tested. Gravimetric and electrochemical measurements were conducted.FindingsCorrelation between inhibition efficiency and calculation of molecular orbital of triazole compounds was obtained. Cu(I)‐triazole complex formation was confirmed by UV spectroscopy.Research limitations/implicationsThe calculation of energetic levels of molecular orbital may be a tool to explain the classification of inhibitor efficiency.Practical implicationsThe theoretical calculation is a complementary mean to selecting an efficient inhibitor among a given series. Good agreement between the experimental methods explored and theoretical calculations was observed.Originality/valueThe originality of this work was the finding of the correlation between energetic levels of orbital molecular and inhibitor efficiency of triazole compounds. The confirmation of the formation of Cu(I)‐triazole by UV‐visible spectroscopy was also new.

PurposeTo evaluate the effect of some tetrazole compounds as corrosion inhibitors of copper in HNO3 at various temperatures.Design/methodology/approach1‐phenyl‐5‐mercapto‐1,2,3,4‐tetrazole (PMT) was selected as the best inhibitor among the tetrazole compounds tested. Gravimetric and electrochemical techniques were conducted.FindingsPMT was an excellent inhibitor for copper in acid. Its efficiency attained 97.5 per cent and decreased slightly with temperature.Research limitations/implicationsThe inhibition efficiency increased with the concentration of PMT to reach 97.5 per cent at 10−3 M. Good agreement between the various methods explored was observed. Polarisation measurements also showed that PMT acted as a mixed inhibitor.Practical implicationsThe efficiency of PMT increased with the concentration but decreased with rise of temperature in the 298‐333 K range. As such, PMT could be used in chemical cleaning and pickling processes.Originality/valueThe originality of this work was the finding of an efficient inhibitor (PMT) having a nearly 100 per cent efficiency.

The comparative study of corrosion behaviour of brasses 70Cu30Zn and 60Cu40Zn in HNO 3 solution in absence and in presence of 1-phenyl-5-mercapto-1,2,3,4-tetrazole (PMT) was studied by gravimetric and electrochemical methods. Results obtained are in good agreement and reveal that the corrosion rate depends on immersion time and zinc content in the alloy. Copper and zinc losses from each specimen studied, at various immersion times, were estimated by Atomic Adsorption Spectroscopic analysis. This shows that the inhibition efficiency of the inhibitor towards copper is more significant than zinc. PMT was adsorbed preferentially on the copper surface and inhibits the process of corrosion of brasses in the nitric acid medium.

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