Purpose
This paper aims to examine the influence of leaves of Cucurbita maxima (LCM) extract on the corrosion of mild steel (MS) in 1N H2SO4 by gravimetric measurement and electrochemical study. The inhibition efficiency increased with increase in concentration of LCM. The corrosion rate increased with increase in temperature and decreased with increase in concentration of inhibitor compared to blank. The maximum inhibition efficiency of 96 per cent was obtained at 3 per cent v/v LCM at 343K for 1 h. The inhibitory action was explained on the basis of adsorption of secondary metabolites in the plant extract on the mild steel surface. The adsorption process obeys Langmuir, El-Awady, Temkin and Freundlich adsorption isotherms and was best fitted by Langmuir adsorption isotherm. Some kinetic and thermodynamic parameters are also discussed.
Design/methodology/approach
Weight loss measurements were conducted under total immersion of already weighed mild steel coupons in 100 ml of the test solution containing 0.05, 0.5, 1, 1.5, 2, 2.5 and 3 per cent of LCM extract and in blank solution at different temperature range (303, 313, 323, 333 and 343 K) for 1h. The electrochemical experiments were conducted at room temperature and at various concentrations of LCM extract. The electrochemical experiments were performed using a potentiostat. A three-electrode cell was used for the impedance measurements conducted at open circuit potential.
Findings
The inhibitor (LCM) shows good inhibition performance for the corrosion of mild steel in 1N H2SO4 solution. The inhibition efficiency increased and the corrosion rate decreased with increasing concentrations of inhibitor.
Originality/value
The studied plant material is a new one in mild steel corrosion. The influence of the plant material is clearly explained in the submitted paper.
The influence of the acid extract of peel of Cucurbita maxima (PCM) on the corrosion of mild steel in 1N H 2 SO 4 was investigated by weight loss, polarization and impedance methods and SEM analysis. The inhibition efficiency increases with extract concentration and immersion period. Weight loss and corrosion rates of mild steel decreased as the concentration of inhibitor increased. The results showed that PCM was potential corrosion inhibitor and maximum inhibition efficiency (IE %) obtained was 98% for 3%PCM at 1h. Impedance measurement results an increase in charge transfer resistance (R ct ), which also confirms the corrosion inhibitive nature of the plant extract. Potentiodynamic study showed that PCM acts as a mixed type of inhibitor, which controls both the anodic and cathodic reactions. Scanning electron microscopic studies provided the evidence of improved surface condition for the corrosion protection, due to the adsorption.
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