Theoretical Study of the Efficiency of Benzo-Phenoxazinone Derivatives in Aqueous Medium to Serve as Effective Organic Corrosion Inhibitors of Mild Steel

The use of inhibitors is one of the most practical methods to protect metals against corrosion, especially in acidic media. Quantum chemical calculations using Austin Model 1 (AM1) semi-empirical method were performed to find the relation between the molecular structure of the inhibitor and the inhibition efficiency and it also compared the inhibition efficiency of benzo-phenoxazinone derivatives with other known organic inhibitor compounds. The following quantum chemical indices were considered: The energy of the highest occupied molecular orbital (EHOMO), the energy of the lowest occupied molecular orbital (ELUMO), separation energy (ELUMO-EHOMO), dipole moment (µ), Log P, and polarizability of the various benzo-phenoxazinone derivatives. The calculated quantum chemical indices confirm that the benzo-phenoxazinone derivatives are potentially effective corrosion inhibitors. The calculated quantum chemical indices also confirm that the benzo-phenoxazinone derivatives actually possess inhibiting properties which are generally more efficient than those of the other known organic inhibitors used in oil and gas systems.