Corrosion inhibition of mild steel in 1 M HCl by sweet melon peel extract

Corrosion inhibition of mild steel by sweet melon (Cucumis melo L) peel (SM) extract in 1 M HCl solution was evaluated by weight loss and potentiodynamic polarization methods. Various SM extracts concentrations such as 0.05, 0.1, 0.2, 0.3, 0.4, and 0.5 g/l were added and corrosion rate (CR) of mild steel and inhibition efficiency (IE) were determined at various temperatures from 295 to 333 K. The appreciable decrease in CR with increase in SM extract concentration was observed at each temperature. However, the typically accelerated CR at each SM extract with the rise in temperature corresponded to the increased kinetic activities at the metal/electrolyte interface. By the addition of 0.5 g/l SM extract, ∼5 times lower CR of mild steel at high temperature (333 K) than in blank acidic solution confirmed its strong inhibitive efficacy. The relatively large variation in the anodic Tafel slope and progressive decrease in CR with an increase in the SM extract concentration validated the restricted dissolution of mild steel. The barrier characteristics of the SM extract layer and its chemical interaction with the surface was evaluated from the low activation energy (Ea) values that fluctuated from ∼20 to 23 kJ/mole. The increase in kad increased from 0.602 to 1.053 (g/l)−1 and decrease in ΔG°ad (−3.74 to −4.91 kJ/mole) with an increase in temperature from 295 to 333 K assured the spontaneous interaction of SM extract molecules with the steel surface.