Inhibition effect of imidazoline and hydropyrimidine derivatives on the corrosion of brass in 0.6 M aqueous sodium chloride solution

摘要

The inhibition effect of o-aminobcnzoic acid (1), p-aminobenzoic acid (2), o-benzenesulphonamidobcnzoic acid (3), p-benzencsulphonamidobenzoic acid (4), 2-(o-benzenesulphonamido)phenylimidazoline (5), 2-(p-ben2enesulphonamido)phenylimidazoline (6), 2-(o-benzcncsulphonamido)phenyl-1,4,5,6-tetrahydropyrimidine (7) and 2-(p-benzenesulphonamido)phenyl-1,4,5,6-tetrahydropyrimidine (8) towards the corrosion of brass in 0.6 M aqueous solution has been studied using potentiodynamic polarization and electrochemical impedance spectroscopy. The corresponding data of 2-(β-benzenesulphonamido)ethylimidazoline (9) and 2-(P-benzenesulphonamido)ethyl-1,4,5,6-tetrahydropyrimidinc (10) are included for comparison. It has been observed that introduction of C6H5-SO2 group increases the inhibition efficiency of aminobenzoic acid by 8-12%. When -COOH group is converted to imidazoline or 1,4,5,6-tetrahydropyrimidine group, the inhibition efficiency is further increased by 7-23%. The inhibition efficiency of these compounds increases in the order :1<3<2<5<4<6<7<8. The inhibition efficiency of 8 with 4 x 10~(-5) M concentration in the highest which reaches 95.4%. The para compounds are better inhibitor than the corresponding ortho compounds due to better surface coverage. The hydropyrimidine derivatives are better inhibitor than the imidazoline derivatives due to more basic character and larger size of the molecules.