Electrochemical and Computational Examination of Camellia Sinensis Assamica Biomolecules Ability to Retard Mild Steel Corrosion in Sodium Chloride Solutions

Abstract

Abstract: Inhibitors are one of the most effective methods for mitigation of metallic corrosion. However, biodegradable inhibitors are being preferred to synthetic inhibitors because of their high competency to suppress corrosion, low-pricing and zero toxicity. In this work, a similar kind of biodegradable material (Camellia Sinensis Assamica) is used for mitigation of mild steel (MS) corrosion in 0.5 M NaCl. Aqueous extract of Camellia Sinensis Assamica (AECSA) is checked for biomolecules by UV–visible and FTIR spectroscopy. The quantification of inhibition efficiency of AECSA is done by weight loss and electrochemical measurements. The maximum inhibition of MS corrosion (85%) is acknowledged with 1000 mg L−1 AECSA. The qualitative inhibition efficiency of AECSA is investigated up to 96 Hr immersion of MS in 0.5 M NaCl by Scanning electron microscopy (SEM) and it is revealed that a layer of AECSA is protecting MS in NaCl solution. The adsorption pattern of AECSA molecules is studied by isotherm fitting and it is found to go with Langmuir isotherm. It is also known through investigation that adsorption occurs in both physical and chemical modes. Furthermore, the adsorption characteristics of AECSA molecules is studied by DFT calculations and it is suggested that the constituent molecules may donate and accept electrons from MS during bond formation, and thus can protect MS in NaCl. Based on total investigation, a mechanism of corrosion inhibition is also proposed. Graphical Abstract: [Figure not available: see fulltext.] © 2021, The Author(s), under exclusive licence to Springer Nature Switzerland AG.