New copper corrosion inhibitors in chloride environments based on [1,2,4]triazolo[1,5-a]pyrimidine-6-carboxylates

The article suggests a new method for the synthesis of new 7-(2-methoxy-2-oxoethyl)-[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxylates containing various substituents at position 2 of the triazolopyrimidine matrix, and describes their structure. The inhibitory effect of the synthesised compounds with regard to copper in neutral and acidic chloride environments is evaluated by means of electrochemical and field corrosion tests and quantum chemical calculations. It was found that all the studied compounds inhibit copper corrosion in neutral and acidic chloride solutions. Generally, the degree of protection monotonously grows with an increase in the inhibitor concentration. The results of the tests in an acidic chloride environment mostly correlate with the corresponding results obtained in neutral aqueous electrolyte solutions and are in good agreement with the data of quantum chemical calculations. The greatest inhibitory effect (over 80%) was observed for 2-mercapto- and 2-amino-derivatives with concentrations of at least 1.00 mM. An inhibitory mechanism is explained as a result of the molecules chemisorption on the metal's surface and the formation of self-organizing protective layers due to the presence of endocyclic NH-protons of the pyrimidine cycle in their structures. The suggested mechanism explains the fact that the inhibitory effect of the studied compounds is observed in the dihydropyrimidine tautomeric forms.