New [1,2,4]triazolo[1,5-a]pyrimidine-7-one corrosion inhibitors for copper in chloride environments

• A.A. Kruzhilin¹, D.V. Lyapun¹, D.S. Shevtsov¹, O.A. Kozaderov¹, A.Yu. Potapov¹, I.D. Zartsyn¹, Ch. Prabhakar² and Kh.S. Shikhaliev¹

¹ Voronezh State University, Universitetskaya pl. 1, Voronezh, 394018, Russian Federation
² National Institute of Technology Kurukshetra, Kurukshetra, 136119, India

Abstract: The article describes a new method for the synthesis of several heterocyclic compounds of the [1,2,4]triazolo[1,5-a]pyrimidine-7-one class. Their structure was proven using NMR spectroscopy and HPLC-MS spectrometry. A series of full-scale natural and electrochemical corrosion tests and quantum-chemical calculations were carried out to study the inhibitory effect of the synthesised substances in relation to copper in neutral and acidic chloride environments within the concentration range of ~0.01–1.00 mM. As a result, it was found that the best protective properties were characteristic of inhibitors containing aliphatic branched butyl, phenethyl, isopentyl substituents (the degree of protection is 81%, 85%, and 90% respectively). The protective effect in their presence increases monotonically with an increase in the concentration of the inhibitor within the solubility limits. The results of tests in an acidic chloride environment generally correlate with the corresponding experiments in neutral aqueous solutions. However, there is an insignificant decrease in the degree of protection. This class of compounds might be less effective in case of acid corrosion of metal. The experimental results obtained and the results of quantum-chemical calculations were used to suggest the most probable inhibitory mechanism. This mechanism consists of the chemisorption of inhibitor molecules on the metal surface accompanied by the formation of self-organising protective layers as a result of the complex formation process with participation of endocyclic NH-protons of the dihydropyrimidine cycle.

Keywords: copper, corrosion inhibitors, chloride corrosion, triazole derivatives, triazolopyrimidines

Int. J. Corros. Scale Inhib., 2021, 10, no. 4, 1474-1492
doi: 10.17675/2305-6894-2021-10-4-7

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