An-Najah Staff

The inhibition of ethyl 2-(4-(2-ethoxy-2-oxoethyl)-2-p-tolylquinoxalin-1(4H)-yl) acetate (Q3) on the corrosion of carbon steel in 1.0 M HCl at 308-343 K was studied by gravimetric method. Results obtained show that Q3 acts as inhibitor for carbon steel in hydrochloric solution. The inhibition efficiency was found to increase with increase in Q3 but decreased with temperature, which is suggestive of physical adsorption mechanism although chemisorption may play a part. The adsorption of Q3 onto the carbon steel surface was found to follow the Langmuir adsorption isotherm. Both kinetic parameters (activation energy, pre-exponential factor, enthalpy of activation and entropy of activation) and thermodynamics of adsorption (enthalpy of adsorption, entropy of adsorption and Gibbs free energy) were calculated and discussed.

Corrosion inhibition efficiencies of 1,4-dihydroquinoxaline-2,3-dione (Q1) and 2-phenylthieno[2,3-b]quinoxaline (Q2) as corrosion inhibitors against the corrosion of steel surface in hydrochloric acid is studied by means of density functional approach B3LYP/6-31G calculations. Quantum chemical parameters such as highest occupied molecular orbital energy (E HOMO), lowest unoccupied molecular orbital energy (E LUMO), energy gap (ΔE), dipole moment (μ), electronegativity (χ), electron affinity (A), global hardness (η), softness (σ), ionization potential (I), the fraction of electrons transferred (∆N), the global electrophilicity ω, and the total energy were calculated. All calculations have been performed by considering density functional theory using the GAUSSIAN03W suite of programs.