Insight into the corrosion inhibition of new benzodiazepine derivatives as highly efficient inhibitors for mild steel in 1 M HCl: Experimental and theoretical study

This work reports the synthesis of two organic compounds based on benzodiazepine derivatives, namely 11phenyl-2,3,4,10,11,11a-hexahydro-1H-dibenzo[b,e][1,4]diazepine (CSBO) and 11-methyl-11-phenyl2,3,4,10,11,11a-hexahydro-1H-dibenzo[b,e][1,4]diazepine (TVBO). The Anti-corrosion properties for mild steel (MS) in molar HCl have been investigated by standard electrochemical and gravimetric methods, the surface of steel and corrosive solutions was analyzed by UV-Visible and Scanning electron spectroscopy (SEM). The experimental results were encouraged by the theoretical calculations (DFT and molecular dynamics (MD) simulations). The results obtained by experimental studies show that both organic compounds are good corrosion inhibitors of mild steel in acidic media, and act as mixed type inhibitors. The thermodynamic parameters show that these two compounds adsorb on the metal surface according to the Langmuir adsorption isotherm. UV-visible spectrometry and the scanning electron microscope show that the addition of the two compounds lowers the dissolution of iron ions in the corrosive solution and forms a protective layer on the surface of the steel. Quantum chemical calculations and MD simulations were used to investigate the correlation between the molecular structure of inhibitors and their corrosion inhibition performances, which agree well with the experimental results.