New promising halogenated cyclic imides derivatives as potential corrosion inhibitors for carbon steel in hydrochloric acid solution

Abstract

In this paper, five new halogenated cyclic imides (1–5) were synthesized with a majority of methanoisoindole-1,3-dione unit through the addition/cyclization reaction of chlorendic anhydride (S1) with a different number of amines. The chemical structures of these new molecules were confirmed by FT-IR (Fourier-Transformed Infrared), 1H NMR, 13C NMR (Nuclear Magnetic Resonance) and Mass spectroscopies. Their performance as corrosion inhibitors, with varying chemical structure, was explored in reducing the corrosion rate of C-steel immersed in 0.5 M HCl solution at different exposure temperatures (25–55 °C) and different concentrations using various types of experimental and theoretical methods such as weight loss, electrochemical, spectroscopic, quantum chemical calculations and molecular dynamic simulations methods. The results indicate the inhibition performance (%IE) of all studied molecules increased with increasing concentration of inhibitors and decreasing solution temperatures. The weight loss method designated that compound 1 showed the best protection productivity of up to 89.6% for carbon steel at 29 × 10−6 M in 0.5 M HCl solutions at 25 °C. The presence of these compounds as inhibitors in the solution increases the charge transfer resistance and reduces the capacity of the double layer. Adsorption of these inhibitors molecules on the C-steel surface obeys the Langmuir adsorption isotherm and acts as mixed-type inhibitors. The results obtained confirm that the theoretical studies are in close agreement with the experimental observations.