Theoretical studies of the effect of structural parameters on the inhibition efficiencies of mercapto-1,2,4-triazoline derivatives

The effect of alkyl and aryl substituents in triazoline compounds on the inhibition efficiency on corrosion has been investigated by molecular orbital calculations using the atom superposition and electron delocalization molecular orbital method. The molecular orbital calculations explain the adsorption of the sulphur-containing inhibitors to the surface through the C-S centre which may be due to the lengthening of the C-S bond length and the increasing of electron density on the sulphur atom and electron deficiency on the carbon atom, It is shown that the aryl-substituted triazolines are more reactive inhibitors than the alkyl ones; this may be due to smaller energy separation between the highest occupied molecular orbital-lowest unoccupied molecular orbital levels. The calculations explain that the presence of electrophilic group shows the highest charge density on the sulphur atom and the highest protection efficiency due to its polar interaction with a metal surface. (C) 2000 Elsevier Science B.V. All rights reserved.