Corrosion mitigation performance of pyrazole derivative on mild steel in acidic media: Electrochemical and theoretical approach

Abstract

• The inhibition effect of 5-Acetyl-2H-pyrazole-3-carboxylic acid ethyl ester (APCE) molecule on the corrosion of mild steel in HCl medium was investigated. • Adsorption of APCE molecule on the metal obeying Langmuir isotherm. • Electrochemical measurement shows the inhibition efficiency around 91%. • SEM and AFM analysis further evidenced by protective film formation. • Structure-property and inhibitor metal interaction proved by DFT approach. Pyrazoles have achieved in recent eras huge prominence because of their effectiveness in obstructing metallic corrosion. Therefore, 5-Acetyl-2H-pyrazole-3-carboxylic acid ethyl ester (APCE) have intended to study as an anticorrosive agent for the metal exposed in 1 M HCl at distinct temperatures. Weight loss, potentiodynamic polarization and electrochemical impedance performances are applied to substantiate the interaction of APCE on the mild steel surface against deterioration. In the Nyquist spectrum, the increase in diameter of a capacitive semicircle indicates the increase in surface coverage capacity of APCE molecules. The maximum displacement of corrosion potential in potentiodynamic polarisation study indicates that the investigated molecule is the mixed-type protector. The inhibitor adsorbed on the deterioration sites of the steel plane follows Langmuir model of adsorption isotherm. Electrochemical measurements confirmed the adsorption of APCE on mild steel with 90.75% corrosion inhibition efficiency at 100 ppm. The increased value of activation energy by the addition of APCE confirms their energy barrier against metal corrosion. Quantum chemical analysis is the supportive evidence for the donation of electrons from inhibitor to Fe plane. SEM and EDS analysis illustrate the construction of a defensive inhibitor layer on the exterior of the metal. A greatly lowered peak height and valley depth value for protected surface in AFM analysis also divulges the topological improvement against surface aggression.