Abstract

The inhibition of corrosion on mild steel in 1M HCl solution was evaluated by utilizing carrot (Daucus carota L.) peels (CP) extract. Study performed by gravimetric and Potentiodynamic polarization techniques. Various concentrations of CP extracts ranging from 0.05, 0.1, 0.2, 0.3, 0.4, and 0.5 (v/v) were used and corrosion rate (CR) on mild steel and inhibition efficiency (IE) were investigated at three temperatures (298K, 308K, and 323K). Corrosion rate increase with the increase in temperature. As inhibitor concentration increases, corrosion rate decreases and IE decreases at elevated temperature. The substantial reduction in CR with the increase in the concentration of CP extract was noted at studied temperatures. However, the increase in the CR at each CP extract along with the increase in the temperature tallied to the increase in kinetic activities at the electrolyte and metal interface. Results show that with the increase of 0.5 g/l CP extract, about 3 times lower CR of mild steel at studied temperatures than in pure 1M HCl solution affirm its robust inhibitive efficiency. Comparatively large change in the anodic Tafel slope and gradual decline in CR with an increase in the CP extract concentration confirmed the restricted dissolution of mild steel. Surface examination suggest that a layer of inhibitor material adsorbed on the surface of mild steel at low temperature is responsible for high IE and this phenomenon is characterized as chemisorption. Weight loss data used to test three well known adsorption isotherm Langmuir, Temkin and Freundlich models and found that data is fitted well to all the models to certain extent however Freundlich Isotherm is found to be best fitted with as the correlation coefficient (R²) values reaching to unity, which showed the applicability of the models to the process.

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