Cinnamaldehyde as a Green Inhibitor in Mitigating AISI 1015 Carbon Steel Corrosion in HCl

This communication reports the inhibitive attributes of cinnamaldehyde mitigating corrosion of AISI 1015 carbon steel in HCl (10% w/w) medium. The mild steel coupons were exposed in HCl medium with and without the presence of cinnamaldehyde. Following the exposure, the samples were analyzed for weight loss, potentiodynamic polarization responses, and postmortem surface characterization. The optimal cinnamaldehyde dose and inhibition efficiency were found to be 200 ppm and 95.36%, respectively. The inhibition was assumed to be mainly due to the adsorption of cinnamaldehyde on the metal surface, which followed the Langmuir isotherm. The temperature effects (25–85∘C\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$85\,{^{\circ }}\hbox {C}$$\end{document}) data suggested that the binding affinity of cinnamaldehyde on the metal surface was strong. The moderate rise of inhibition efficiency was associated with the chemical adsorption. The value of activation energy (Ea)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$(E_{\mathrm{a}})$$\end{document} obtained was found to be lower than that the value obtained in the inhibitor-free HCl solution. The polarization measurements showed that the inhibitor was virtually mixed type with reduction of cathodic and anodic current densities. The inhibition efficiency, calculated from weight loss and potentiodynamic polarization, was found to be in good agreement with the literature. Scanning electron microscope observations confirmed the existence of a protective adsorbed film of the inhibitor on the metal surface.