Effect of Black Carrot (Daucus carota subsp. Sativus) Extract on Corrosion of Mild Steel in Acidic Medium

Abstract: This study investigates the corrosion inhibition efficiency of black carrot (Daucus carota subsp. sativus) extract on mild steel in a 1M HCl solution. Electrochemical methods, including potentiodynamic polarization and electrochemical impedance spectroscopy (EIS), were employed to evaluate the protective effects of the extract at various concentrations. The results reveal that the black carrot extract significantly reduces the corrosion rate of mild steel, with the inhibition efficiency reaching up to 93% at a concentration of 50 mL. The polarization data indicated a notable decrease in corrosion current density (icorr) and a shift in corrosion potential (Ecorr), suggesting the extract acts as a mixed-type inhibitor. Adsorption studies confirmed that the inhibition mechanism follows the Langmuir adsorption isotherm, with adsorption likely occurring via physical and chemical interactions. The extract's efficacy in mitigating corrosion is attributed to the presence of polyphenolic compounds, particularly anthocyanins, which form a protective film on the metal surface. Additionally, temperature and immersion time studies demonstrated that the inhibition efficiency decreases with increasing temperature but remains effective over prolonged immersion periods. Scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) further supported the formation of a protective layer on the mild steel surface. These findings suggest that black carrot extract is a promising eco-friendly corrosion inhibitor for mild steel in acidic environments.