The inhibitive effect of Curry leaves extract (CLE) on the corrosion behavior of aluminum in sulfuric acid (pH = 3) was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques in the temperature range of 30 °C to 50 °C. The study was done by varying the concentrations of inhibitor from 0.05 g L−1 to 0.4 g L−1. The surface morphology was studied using scanning electron microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDX). Inhibition efficiency was found to increase with increase in inhibitor concentration and decrease with increase in temperature. CLE acted as an anodic type inhibitor at lower concentrations of inhibitor and behaved as a mixed type at higher concentrations of inhibitor and underwent both physisorption and chemisorption on the surface of the metal and followed the Langmuir adsorption isotherm.
Inhibition of aluminum corrosion in 1M HCl in absence and presence of three compounds of non ionic surfactants compounds derived from phenol was investigated using hydrogen evolution reaction, weight loss galvanostatic polarization and electrochemical impedance spectroscopy techniques. It was found that the percentage inhibition increases with increasing the concentration of inhibitor, amount of ethylene oxide unit and with decreasing temperature. The inhibitive action of non ionic surfactant compounds was explained in terms of blocking the electrode surface by adsorption process. The adsorption process follows Langmuir isotherm. The polarization measurements showed that these inhibitors are acting as mixed inhibitors for both cathodic and anodic reaction. Electrochemical impedance spectroscopy technique exhibit one capacitive loop indicating that, the corrosion reaction is controlled by charge transfer process. Some activated thermodynamic parameters are calculated and explained.
The influence of water-soluble poly (vinyl alcohol) (PVA) as a synthetic polymer containing secondary alcoholic groups on the rate of dissolution of aluminum (Al) metal in alkaline medium has been investigated using both gasometric and weight-loss techniques. The results showed that addition of poly (vinyl alcohol) to the tested solutions leads to a remarkable decrease in the corrosion rates of Al in alkali. The magnitude of inhibition efficiency was determined and compared to that obtained with other macromolecules containing secondary alcoholic groups. The inhibition action of PVA on Al metal surface was found to obey Freundlich adsorption isotherm. Factors affecting the corrosion process such as the concentration and nature of the inhibitor, concentration of the corrosive medium and the temperature were examined. A tentative inhibition mechanism consistent with the kinetic results obtained is suggested and discussed.