Investigation of the inhibitory activity of some 3-aryl(hetaryl)-5- amino-1H-1,2,4-triazoles on copper chloride corrosion

The article describes an example of applying the principles of molecular design to develop new organic corrosion inhibitors.Methods for the synthesis of 3-aryl/hetaryl-5-amino-1H-1,2,4triazoles have been developed, and the influence of substituent nature at the 3rd position in the molecules of 1,2,4-triazoles on their inhibitory activity towards copper corrosion in chloride solutions (1% HCl) has been investigated.The research on a series of 3-aryl/hetaryl derivatives of 5-amino-1,2,4-triazole revealed that the anti-corrosive properties of substances in this class substantially depend on the structure of the aromatic substituent.Direct corrosion tests in chloride solutions have shown that 3-(pyridin-3-yl)-1H-5-amino-1,2,4-triazole 2d and 3-(thiophen-2-yl)-1H-5-amino-1,2,4-triazole 2f, at a concentration of 0.01M, provide copper protection levels of 87.7% and 85.9%, respectively.We suggest that the maximum protective effect of pyridin-3-yl-5-amino-1,2,4-triazole 2d is due to the fact that the pyridine, attached to the basic triazole matrix in the 3rd position, acts as a strong electron density acceptor, increasing the acidity of the nitrogen endo-atom in the triazole and facilitating the formation of more stable complexes with copper atoms.Quantum chemical calculations revealed that the presence of a pyridin-3-yl substituent in the structure of aminotriazole leads to the lowest values of HLG, which is also considered indirect evidence of high protective properties in homologous series of inhibitors adsorbed on the metal surface.The high protective effect of pyridin-3-yl-5-amino-1,2,4-triazole was demonstrated using SEM microscopy.