New Schiff's bases with 1,2,4-triazole ring (3a-j) have been synthesized from 4-(4'-amino-5-mercapto-4H-1, 2, 4-triazol-3-yl) phenol (2) which is obtained from 4-hydroxybenzohydrazide (1) by a cyclization reaction as shown in (scheme 3-1). Infrared spectroscopy and 1H NMR spectroscopy were used to characterize the structures of synthesized compounds. All the final products are indicated as thione-thiol tautomers.The Corrosion inhibition of prepared compounds (2 (and (3a-j (have been studied on mild steel in one molar sulfuric acid solution at 25 oC. Weight loss method was used to evaluate the inhibition efficiency of the above compounds. Results indicate that the inhibition efficiency IE% increases with increasing inhibitor concentration. Results indicated also that six compounds (3b, 3d, 3e, 3f, 3h, and 3j) exhibited at least 87.8 % IE with the minimum inhibition concentrations about 5*10-5 M. This excellent inhibition efficiency may attributed mostly to the presence of heteroatoms attached to benzene ring substituents derived from introduced benzaldehyde derivatives (p-OH, p-Br, o-NH2, p-CH3, p-OCH3, and o-OH). High Planarity of the synthesized molecules may have been the main reason for the strong adsorption of the molecules on the metal surface.
