N-pyridinium salt derivatives (1), (2), (3), (4) and (5) were prepared and their inhibition effect as corrosion inhibitors for mild steel was investigated in 1 M H 2 SO 4 solution at 30 o C for 24 hs. The corrosion inhibiting action was studied using weight loss measurements. The results have revealed that the corrosion rate decreases, inhibition efficiencies increase and surface coverage degree increases with a higher inhibitor's concentration. Inhibition efficiencies for prepared N-pyridinium salt derivatives have the highest inhibiting efficiency even for a low concentration. The values of ∆G o ads are showing physisorption effect for all prepared compounds. Molecular modeling systems were achieved for the suggested inhibitors (1), (2), (3), (4) and (5). Theoretical calculations could be used as a useful tool to obtain information for explaining the mechanism and nature of interaction between the metal surface and the organic molecule as a corrosion inhibitor.Keywords: corrosion inhibitor, inhibition efficiencies, physisorption, molecular modeling. IntroductionCorrosion of materials has kept getting significance in the wide fields of technology. Corrosion inhibition researches are assiduous to find variant and efficient ways of protecting the metals against corrosion. The mechanistic basis of corrosion inhibitors depends on the specific interaction between certain atoms in the inhibitors with the corroded sites on the metal surface. These atoms, such as nitrogen, oxygen and sulphur have a main role in this interaction via donating their free electron pairs [1,2]. Schiff bases found interest applications as corrosion inhibitors in carbon steels [3,4], and other metals [5,6]. Literature has revealed that alkyl quaternary ammonium compounds are important as inhibitor additives in acidic media to reduce the corrosion process of iron and steel [7,8].

N-pyridinium salt derivatives (1-5) were prepared and investigated as corrosion inhibitors for mild steel in 1 M H 2 SO 4 solution at 30°C for 24 h. The corrosion inhibiting action was studied using weight loss measurements. The results demonstrated that the corrosion rate decreases, inhibition effi ciencies increase, and surface coverage degree increases with increasing inhibitor concentration. Inhibition effi ciencies for prepared N-pyridinium salt derivatives have highest inhibiting effi ciency for even low concentration. The values of ∆G°a ds showed physisorption effect for all prepared compounds. Molecular modeling systems were achieved for suggested inhibitors 1-5. Theoretical calculations could be used as a useful tool to obtain information for explaining the mechanism and nature of interaction between the metal surface and the organic molecule as a corrosion inhibitor.