The corrosion inhibition efficiency of thiophene-2-carbaldehyde tryptophan (T2CTRY) on mild steel (MS) in 1 M HCl solution has been investigated and compared using weight loss measurements, electrochemical impedance spectroscopy, and potentiodynamic polarization analysis. The Schiff base exhibited very good corrosion inhibition on mild steel in HCl medium and the inhibition efficiency increased with the increase in concentration of the inhibitor. The adsorption of the inhibitor on the surface of the corroding metal obeys Freundlich isotherm. Thermodynamic parameters (K ads , ΔG 0 ads ) were calculated using adsorption isotherm. Polarization studies revealed that T2CTRY acts as a mixed type inhibitor. A maximum of 96.2% inhibition efficiency was achieved by EIS studies at a concentration of 1 mM. Experimental2.1. Inhibitor. Heterocyclic Schiff base T2CTRY was synthesized by the condensation of equimolar mixture of thiophene-2-carbaldehyde and tryptophan in ethanol medium. The reaction mixture was refluxed for 3 hours, concentrated, and cooled. The yellow coloured solid was filtered, washed, and dried. Figure 1 shows the molecular structure of the heterocyclic Schiff base T2CTRY. Anal. calcd. for C 16 H 14 N 2 O 2

The corrosion inhibition efficiencies of two novel Schiff bases, namely (E)-3-[thiophen-2-ylmethyleneamino]benzoic acid (T2YMABA) and (E)-4-(5-[(2-phenylhydrazono) methyl]thiophen-2-yl)benzoic acid (PHMT2YBA) on mild steel (MS) in 1.0M HCl solution has been investigated and compared using electrochemical impedance spectroscopy and potentiodynamic polarization analysis. The Schiff bases exhibited very good corrosion inhibitions on mild steel in 1.0M HCl medium and the inhibition efficiency increased with the increase in concentration of the inhibitor. Polarization studies revealed that T2YMABA acted as a mixed type inhibitor whereas PHMT2YBA molecules acted as anodic inhibitor.

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Heterocyclic compound 3-acetylpyridine phenylhydrazone (APPH) and its copper chelate were synthesized and characterized by spectral, elemental, magnetic and conductance measurements. Investigations showed that APPH behaved as bidentate ligand during chelation. The square planar geometry of the chelate was confirmed by magnetic and optical spectral studies. The detailed electrochemical response of the ligand and chelate were evaluated and reported.