QUANTUM-CHEMICAL MODELING (QCM) AND QUANTUM STRUCTURE-ACTIVITY RELATIONSHIP MODELING (QSARM) OF ACID PICKLING INHIBITION

Abstract

The effect of six organic compounds, saccharin, three alkynylenediols and two quaternary pyridinium salts, on the inhibition of corrosion of steel in two acids, 6.3 N hydrochloric acid and 4.28 N sulfuric acid, was investigated using weight loss measurements. The inhibiting efficiencies varied between 0.016 and 0.98. The structures of organic compounds were geometrically optimized. Then, using the ab initio and PM3 methods, the energies of molecular orbitals were calculated, as were the structural values (QSAR) of these compounds. The theoretical results obtained were correlated with experimental data. Finally, multiple regression with I _r as the dependent variable was obtained for two acids together and the best was the regression for the three independent variables. Quantum-chemical calculation with the PM3 semi-empirical method and QSAR calculations for nine amines used by Babu and others to etch steel in 1 M hydrochloric acid were also performed. These model calculations seem to be useful to evaluate etching inhibition in 1 N hydrochloric acid, which can be assured by the studied amines.

Key Words:

• Inhibition
• Acid pickling
• Modeling
• Adsorption
• Organic

Notes

Note: HOMO, LUMO calculated using the semi-empirical PM3 method.

Note: The value of HOMO energy for Fe is −5.78eV, of LUMO energy, 2.65eV.

^ap > 0.05

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