| Summary: | Two tridentate hydrazone ligands (AL01, AL02) were synthesized by condensation of an aldehyde and two hydrazides, benzohydrazide and 2-hydroxybenzohydrazide with OH substituent at the ortho position of the benzene ring. They were characterized using melting point, FTIR, NMR, elemental analysis, UV-Vis as well as mass spectroscopy. The formation of hydrazone ligands was confirmed by the appearance of v(C=N) peak in the range of 1608 to 1648 cm-1. The significant peak of N-H protons for AL01 and AL02 appeared at 8.82 and 8.41 ppm respectively, while the peak of phenolic proton (O-H) for AL01 was found at 12.28 ppm. Two peaks were observed in the wavelength range of 198-220 nm that can be attributed to π-π*(C=C) and n-π*(C=C) transitions of aromatic benzene, while the peaks for π-π*(C=N) were observed in the range of 297–303 nm. The mass-to-charge (m/z) [M+H]+ values of AL01 and AL02, which are 242.09 and 226.10, respectively, further confirmed their structures. The effectiveness of hydrazone ligands as corrosion inhibitors on mild steel in 3.5% NaCl solution saturated with CO2 was examined using polarization and electrochemical impedance spectroscopy (EIS). The elemental constituents of the protective layer forms on mild steel immersed in the solution were further observed using scanning electron microscopy (SEM) coupled with energy-dispersive X-Ray (EDX)). Therefore, new corrosion inhibitors of tridentate hydrazone ligands, AL01 and AL02 were successfully synthesized and characterized using FTIR, NMR, elemental analysis, mass spectroscopy and UV-Vis. From polarization and EIS study, AL01 can be concluded to have higher inhibition efficiency, 84.30% at 500 ppm concentration compared to AL02, 74.90%. SEM-EDX analysis has confirmed the formation of the inhibitors’ layer on mild steel as the surface of the mild steel immersed in solution with the presence of inhibitors have a smoother surface compared to that of untreated mild steel in 3.5% NaCl solution saturated with CO2. © 2024, Malaysian Society of Analytical Sciences. All rights reserved.
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