M.A. Deyab

Experimental and Theoretical Investigations of Adsorption andInhibitive Properties of Tween 80 on Corrosion of Aluminum Alloy(A5754) in Alkaline Media

Abstract The inhibition behavior of Polyoxyethylene (20) sorbitan monooleate (Tween 80) as a non-toxic corrosion inhibitor for aluminum alloy (A5754) was investigated in 0.5 M NaOH solution by means of polarization measurement and quantum chemistry method. A significant inhibition in the corrosion rate of A5754 in NaOH solution was observed in the presence of Tween 80. As a result of adsorption of the inhibitor on the metal surface, the inhibition of this compound increases with its concentration but decreases with temperature. Polarization curves showed that Tween 80 acted as mixed inhibitor. The adsorption of Tween 80 obeys the Langmuir adsorption isotherm. Comprehensive adsorption (physisorption and chemisorption) of the inhibitor molecules on the A5754 surface was suggested based on the thermodynamic adsorption parameters. Correlation between quantum chemical calculations and inhibition efficiency of the investigated compounds was discussed using DFT method.

Influence of Nonoxynol-9 on the Corrosion Inhibition of Carbon Steel in 1.0 M Hydrochloric Acid Solution

Abstract The inhibitory performance of nonoxynol-9 (N9) as a corrosion inhibitor for carbon steel was evaluated in 1.0 M HCl solution at different temperatures. Potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and quantum chemical calculation methods were used in this study. The results indicated that the corrosion rate decreased with increasing concentration of N9 up 150 ppm and decreased with the increase in temperature of the medium. The comparison between the results obtained by polarization and EIS methods showed a good agreement. The corrosion inhibition effect of N9 could be related to the adsorption of N9 molecules on the metal surface. Polarization curves indicated that N9 behaves as a mixed type inhibitor. EIS exhibited one capacitive loop which indicates that the corrosion reaction is controlled by charge transfer process. The inhibition mechanism of N9 involves physical interaction between the inhibitor and metal surface. The adsorption of N9 on carbon steel affords physisorption process and obeyed the Langmuir adsorption isotherm.

Corrosion and Corrosion Inhibition of Aluminum Alloys A5052 and A5754 in Sulfuric Acid Solutions by Some Inorganic Inhibitors

Abstract The corrosion of aluminum alloys (A5052 and 5754) in sulfuric acid solutions was investigated using potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM), and energy-dispersive X-ray (EDX) methods. For comparison, the corrosion of pure aluminum in sulfuric acid was examined potentiodynamically. The data reveal that increasing sulfuric acid concentrations and solution temperature enhance the corrosion rate of aluminum alloys. The two aluminum alloys exhibit higher corrosion resistance than pure aluminum. Moreover, A5052 involves more corrosion resistance than A5754. The effect of WO2−4 and MoO2−4 anions as inorganic inhibitors on the corrosion of aluminum alloys in 0.3 M H2SO4 solution has also been studied. Results show that the presence of either WO2−4 or MoO2−4 anions in the acid solution decreases the corrosion of aluminum alloys. The Langmuir isotherm is found to be an accurate isotherm describing the adsorption of these oxyanions on the alloys surface.

Improved Corrosion Resistance of Aluminum in 0.5 M HCl Solution using Plasma Electrolytic Oxidation

Abstract In this paper, the plasma electrolytic oxidation (PEO) was used to improve the corrosion resistance of aluminum in 0.5 M HCl solution. Influence of many factors such as the composition of electrolytes, time and inorganic additives on the performance of PEO process have been investigated. The surface morphology of PEO films was inspected using SEM, EDX and XRD analysis. The electrochemical impedance spectroscopy (EIS) and polarization measurements were carried out to evaluate the corrosion resistance of aluminum. The hardness and reduced modulus of aluminum surface at different PEO process time were determined by nanoindenter measurements. The results showed that the best conditions for formation high efficient oxide layer on the aluminum surface during PEO process were carried out in 0.001 M NaOH electrolyte containing 9 × 10−5 M Na2WO4 for 5 min. The PEO process is able to inhibit uniform and pitting corrosion of aluminum in HCl solution. The surface morphology analysis showed that PEO process produce a highly resistant protective oxide layer, mainly composed of orthorhombic crystalline phase of α-Al2O3. This oxide characterized by its greater hardness.

Estimation of the Inhibition Efficiency of Polysorbate 80 Against the Corrosion of 6061 Aluminum Alloy in Di-Sodium Hydrogen Orthophosphate Solution

Abstract The inhibiting behavior of polysorbate 80 on 6061 aluminum alloy corrosion was evaluated in 1.0 M Na2HPO4 solution. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques were used in this study. The obtained results showed that the inhibition efficiency increases by increasing the concentration of polysorbate 80 reaching 85.8% at 500 ppm. Good agreement was found between the results obtained from the two techniques used. The inhibition process was found to be due to adsorption of the organic compound on the alloy surface obeying the Langmuir isotherm. Polarization curves indicate that the inhibition of polysorbate 80 has the mixed anodic–cathodic nature. EIS exhibits one capacitive loop which is attributed to the double layer charging and the charge transfer process. The inhibition efficiency of polysorbate 80 decreased by rising the temperature in the range of 303–333 K. These results confirm the physisorption of the inhibitor molecules on the metal surface. The thermodynamic functions for the dissolution and adsorption processes were calculated and discussed.