The inhibitory effect of imidazo [1,2-a] azepinium bromides on corrosion of carbon steel in hydrochloric acid medium

Abstract

The mechanism of corrosion protection of mild steel by imidazo [ 1,2-aJ azepinium bromides was considered in this woik. These compounds are effective inhibitors of carbon steel corrosion in acid chloride medium. Their high protective action manifests itself within the temperature range of 293 to 333 K. The inhibition efficiency measured by means of gravimetric method at 293 K is 93.0-96.8%, it changes insignificantly with the temperature. The inhibition properties of the compounds are caused by the formation of a protective film of up to 4 nm thickness on the carbon steel surface, which is demonstrated by Auger electron spectroscopy. The chemisorption of the inhibitors molecules also ensures considerable protective aftereffect. The correlation between the inhibition efficiency and molecules energy characteristics, in particular the difference in energy values of tower vacant and higher occupied molecular orbitals, was determined. The possible realization of macrocycle effect was shown under the chemisorption of the inhibitors, molecules of which have four negatively charged adsorption-reaction centres and present a formed chelate bond.