Electrochemical, Quantum Chemical and Surface Analysis Studies using Novel Schiff Bases for the Inhibition Mild Steel Corrosion in Sulphuric Acid Medium

M. Ragu1,, P. Karuppasamy2,, J. Thirupathi3,, M. Ganesan4,, T. Rajendran5, and V.K. Sivasubramanian1,*,

1PG and Research Department of Chemistry, Vivekananda College, Tiruvedakam West, Madurai-625234, India

2Department of Chemistry, Dayananda Sagar College of Engineering, Bangalore-560078, India

3Department of Chemistry, Thiagarajar College, Madurai-625309, India

4Department of Chemistry, Sri Vidhya College of Arts and Science, Virudhunagar-626005, India

5Department of Chemistry, K.L.N. Arts and Sciences College, Pottapalayam, Sivagangai-630612, India

*Corresponding author: E-mail: sivavk1957@gmail.com; mragu@vivekanandacollege.ac.in

Abstract

The influence of two newly synthesized salophen Schiff bases, namely N,N′-bis(5-nitrosalicylidene)-1,2-phenylenediamine (BNSPD) and N,N′-bis(5-chlorosalicylidene)-o-phenylenediamine (BCSPD), for inhibiting mild steel corrosion was investigated using potentiodynamic polarization, weight loss and electrochemical impedance spectroscopy in 0.5 M H2SO4 media. The results indicated that the inhibition efficiency of the inhibitors increased and decreased with the increase in the inhibitor concentration and temperature, respectively. Potentiodynamic polarization measurements revealed that the two inhibitors exhibited mixed type. The standard free energy (Δads) and equilibrium constant of adsorption (Kads) were calculated. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques were used to investigate the surface morphology of the mild steel in the absence and presence of inhibitors. DFT calculations were performed to correlate the molecular structure and quantum chemical parameters with inhibition performance.

Keywords

Corrosion inhibitors, Mild steel, Salophen, Schiff bases, Thermodynamics, Adsorption isotherms.

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