The Inhibitory Properties of the Ambroxol Derivative on the Corrosion of Mild Steel in Hydrochloric Acid Medium

A compound 2-(6,8-dibromo-3-(4-hydroxycyclohexyl)-1,2,3,4-tetrahydroquinazolin-2-yl)phenol was synthetised from ambroxol hydrochloride and salicylaldehyde. The structure of the compound was studied with UV, IR, Raman, and 1H NMR spectroscopy. The inhibitory ability of the synthetised compound on the corrosion of mild stainless steel EN Fe37-3FN in 0.5 M hydrochloric acid solution was studied using gravimetric and electrochemical methods, including potentiodynamic polarisation and EIS. It was shown that the inhibitory activity of the compound increases with the increase of its concentration in a solution. An addition of 3 mg/l of the compound reduces the corrosion rate by 20% and that of 400 mg/l by 85%. The data of gravimetric and electrochemical measurements coincide well. The sorption of the compound on the metal surface obeys the Langmuir adsorption isotherm, and the nature of adsorption is physical. The compound exhibits the chelating activity with both ferrous and ferric ions in the acidic solution. The synthetised compound may be a good choice for the inhibition of steel corrosion in acidic environments.