Synthesis and anticorrosive properties of 2-alkyl-5-methyl-4,5,6,7- tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidin-7-ols
Abstract
Objectives: The aim of the study is to synthesize a series of 2-alkyl-5-methyl-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a] pyrimidin-7-ols, to investigate their inhibitory properties and the regularities of their interaction with a steel surface, in order to create a new generation of efficient and environmentally friendly acid corrosion inhibitors.
Experimental: The paper presents the results of synthesis and investigation of the anticorrosion properties of new 2-alkyl-5-methyl-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidin-7-ol derivatives obtained from individual fatty acids and vegetable oils. The reaction of aminotriazoles with crotonaldehyde in an amphoteric surfactant medium made it possible to develop a method for producing the target compounds with high yield and purity. The anticorrosion properties of the synthesized triazolopyrimidinol derivatives were studied with respect to St3 steel in 24% HCl using both direct methods (GOST 9.905-82, 9.907-83) and electrochemical techniques (potentiodynamic polarization and polarization resistance method according to Mansfeld). Electrochemical tests by potentiodynamic polarization and direct corrosion measurements
in 24% HCl showed that all investigated compounds exhibited a pronounced inhibiting effect on St3 steel.
Conclusions: It has been established that all investigated compounds act as mixed-type inhibitors. The most effective ones were the derivatives obtained from coconut oil, providing protection efficiencies up to 98.5% at concentrations of 1–2 g/L. Comparison of gravimetric and polarization data revealed that the high instantaneous protection efficiencies determined by electrochemical methods correspond to intensive physical adsorption of inhibitor molecules immediately after their introduction. However, during prolonged exposure in direct gravimetric tests, a decrease in protection efficiency was observed for compounds with alkyl substituents of C13 and longer, which is attributed to the partial instability and desorption
of the protective films under extended acid exposure. This leads to localized corrosion on certain surface areas and a reduction in the overall protection efficiency. The results confirm the promise of synthesizing 4,5,6,7-tetrahydro-[1,2,4] triazolo[1,5-a]pyrimidin-7-ols from renewable plant-based feedstocks for the development of biodegradable acid corrosion inhibitors.
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