Corrosion inhibition, adsorption behaviour and thermodynamic properties of N-cinnamalidene palmitohydrazide on mild steel in hydrochloric acid solution
2020
Nor Azowa Ibrahim | Yeong, Shoot Kian | Chan, Chung Hung | Tang, Sook Wah | Noor Khairin Mohd | Lim, Wen Huei | Siti Mariam Mohd Nor | Zainab Idris
The corrosion inhibitory efficiency of N-cinnamalidene palmitohydrazide (CPH) on mild steel in 1 M hydrochloric acid solution was studied using Tafel polarisation, electrochemical impedance spectroscopy and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX). Tafel polarisation analysis showed that the maximum inhibition efficiency (ηTafel%) approached 95% in the presence of 200 mg litre-¹ of CPH at 328K. The percentage inhibition efficiency increased with increasing inhibitor concentration and temperature of the test medium. Tafel polarisation study clearly revealed that CPH functions as a mixed-type inhibitor with a predominant anodic control. The adsorption of CPH on mild steel surface obeyed the Langmuir’s adsorption isotherm. The evaluation of the thermodynamic and activation parameters indicated that the adsorption of CPH on the mild steel surface took place spontaneously through both physisorption and chemisorption with Gibbs free energy of adsorption (ΔGºads) values from -34.33 kJ mol-¹ to -41.38 kJ mol-1. Impedance spectroscopy analysis showed that corrosion of mild steel in 1 M hydrochloric acid solution was mainly controlled by a charge transfer process and CPH formed a protective film on the metal-solution interface. The protective film was further confirmed by SEM images and the elemental analysis that measured by EDX analysis.
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