Investigation of transition metal chelates with a ligand (3-cyano-6-thiophen-2-yl[4,4′]bipyridinyl-2-yloxy)-acetic acid hydrazide as corrosion inhibitors for copper in 1.0 M HCl solution

Abstract

Mn(II), Fe(III),Co(II), Ni(II) and Cu(II) complexes of the ligand named (3-Cyano-6-thiophen-2-yl[4,4′]bipyridinyl-2-yloxy)-acetic acid hydrazide (abbreviated as HL) have been synthesized. Structure assignment of such chelates have been performed by means of analytical and spectral tools which joint assured the formulation of the chelates in 1 M: 1 L ratio with non-electrolytic character for all the complexes. Fe(III) complex is 1:3 electrolyte. The spectral IR toll proved the neutral tridentate ligand nature connecting to the metal ions by the azomethine nitrogen, carbonyl and ester oxygen atoms. Octahedral structure has been concluded for all the isolated chelates as deduced from the UV-Vis spectral analysis. The investigated complexes were tested to protect or restrain the corrosion of copper in 1.0 M HCl solution at 298 K using different techniques. The outcomes being acquired illuminated that the synthesized compounds were discovered to be efficient inhibitors and their % IEs were concluded to be dependent on both concentrations and structures. The order of the % IEs of the tested compounds was: HL-Mn> HL-Fe> HL-Co ≥ HL- Ni> HL-Cu> HL. The acquired high % IEs were ascribed to the powerful adsorption of the organic molecules on the surface of copper which was agreed with Langmuir adsorption isotherm. The kinetics of corrosion inhibition by the examined compounds appeared negative-first order process. PDP results indicated that the complex HL-Mn behaves as a mixed-kind inhibitor with slight anodic seniority. The employed techniques used for the complex HL-Mn were in a good consistence with each other.