Synthesis, Characterisation and Corrosion Inhibition of Mild Steel by Butyltin(IV) 2-Acetylpyridine 4-Methyl-3-Thiosemicarbazone in HCl

Abstract

Schiff base ligand, 2-acetylpyridine 4-methyl-3-thiosemicarbazone (Me-LH), and its organotin complex (BuSn(Me-LH)Cl2) were synthesized, characterized, and subjected to corrosion inhibition study. The spectra and crystal structure obtained revealed that the ligand is coordinated by pyridyl nitrogen, azomethine nitrogen, and thiolate sulfur to organotin (IV) ion. Corrosion inhibition of the synthesized compounds on mild steels in 1 M HCl solution at different concentrations were tested using weight loss, Electrochemical Impedance Spectroscopy (EIS), potentiodynamic polarization, Scanning Electron Microscopy (SEM) and adsorption analyses. Corrosion inhibition results showed that the complex had a strong corrosion inhibitory effect in comparison to the ligand. The inhibition efficiency of all the techniques improved with an increase in the concentration of corrosion inhibitor. Polarization analysis results showed that the compounds can be categorized as mixed-type inhibitors. Meanwhile, the EIS study indicates that with an increase in the concentration of corrosion inhibitor, the resistance to charge transfer increased. This resulted in the adsorption of inhibitors and the development of a protective layer on the mild steel surface which was further confirmed by SEM analysis. The adsorption isotherm of compounds on a mild steel surface followed the Langmuir isotherm model.
 HIGHLIGHTS
 
 The efficient method to inhibit the corrosion rate of mild steel in an acidic medium is a corrosion inhibitor
 The electrochemical and weight loss analysis proved that the corrosion inhibition efficiency increases when the concentration of inhibitor is increased
 The study proved that the thiosemicarbazone complex showed the potential as corrosion inhibitors at low concentrations
 
 GRAPHICAL ABSTRACT