Elsholtzia Griffithii as an eco-friendly anticorrosive inhibitor of Mild Steel under Acid Medium

Abstract

Anticorrosion analysis of Elsholtzia Griffithii extract on Mild Steel (MS) in H2SO4 medium was experimented with through Gravimetric Method, Potentiodynamic Polarization, Electrochemical Impedance Spectroscopy (EIS) at room temperature. Results of the assessment showed that Elsholtzia Griffithii inhibits the corrosion of MS and the rate of corrosion is significantly reduced on increasing its concentration. Elsholtzia Griffithii exhibits the rise in its anticorrosive efficiency from 82.0% to 95.0% when the extract's concentration altered from 125 mg/L to 1000 mg/L. The variation in Ecorr value is within 85 mV, revealing Elsholtzia Griffithii as a mixed-type inhibitor. The change of charge transfer resistance (Rct) from 4.90 Ω cm−1 to 96.92 Ω cm−1 with falling of double layer capacitance (Cdl) from 947.22 × 10−4 F cm−2 to 2.74 × 10−4 F cm−2 on the addition of extract is a clear indication of the mitigation of corrosion. The corrosion mitigation is caused by the adsorption of extract molecules on surface of MS and Langmuir's adsorption isotherm is obeyed in its mechanism of adsorption. The results of gravimetric and electrochemical methods are concurred by the observation of Gas Chromatography Mass spectrometry (GC-MS), Fourier transform infrared (FTIR), UV-VIS spectroscopy and Scanning electron microscopy (SEM) studies. The functional groups such as O-H, CO and CC in the extract are responsible for binding on the mild steel surface. Density Functional Theory (DFT) calculation was further carried out to validate the experimental results. All the findings suggested that Elsholtzia Griffithii is a tenable and sustainable inhibitor for corrosion of MS under acid solution.