A.S. Fouda

The role of some thiosemicarbazide derivatives in the corrosion inhibition of aluminium in hydrochloric acid

Abstract The inhibitive action of some thiosemicarbazide derivatives towards the corrosion of aluminium in 2 M HCl has been investigated by using thermometric, weight loss and hydrogen evolution techniques. The three independent techniques gave similar results. The inhibitors used were found to be weakly adsorbed on the aluminium surface through a one-step process. The order of inhibition efficiency of the inhibitors used depends on the number of adsorption sites in the molecule and their charge density, molecular size, heat of hydrogenation and formation of metallic complexes.

The role of indole and its derivatives in the pitting corrosion of Al in neutral chloride solution

The ability of indole and its derivatives to protect aluminium against pitting corrosion was studied using potentiodynamic polarization technique. The order of inhibition effect of these compounds was found to be tryptamine (II) > tryptophane (III) > indole (I). The current decay measurements were used to confirm the inhibiting characteristics and the order of inhibition effect of these compounds. The inhibition properties of these compounds were discussed according to their adsorption on Al surface. The inhibition efficiency was found to be depending upon the number of active centres, molecular size and the mode of adsorption. The effect of preadsorbed film of these compounds on the pitting corrosion of Al was also studied. Finally, their influence on the ethanol oxidation was tested using cyclic voltammetric technique. The results were discussed and correlated to the their inhibition properties towards Al pitting corrosion.

The effect of some B-diketo compounds on the retardation of aluminium dissolution in HCl

Abstract The inhibitive action of some B-diketo compounds on the dissolution of aluminium in 2M HCl has been investigated by hydrogen evolution, thermometric and weight loss techniques. The adsorbability of inhibitors is dependent on the basicity of the oxygen and nitrogen sites involved. The dissolution reaction of aluminium in hydrochloric acid solutions is zero order and remains so when B-diketo compounds are present. The rate constant decreases as the inhibition efficiency increases. The activation energy of the dissolution reaction increases with decreasing acid concentration and increasing inhibitor concentration. Values of the Arrhenius activation energies agree with those obtained for an activation controlled process.

INHIBITION OF CARBON STEEL CORROSION BY SOME CYANOACETOHYDRAZIDE DERIVATIVES IN HCl SOLUTION

This article describes an investigation of the corrosion behavior of carbon steel in 2 M HCl solution with the addition of some cyanoacetohydrazide derivatives by weight loss, galvanostatic polarization, and potentiodynamic anodic polarization techniques. The explored methods gave almost similar results. Results obtained reveal that inhibitor (I) is the best inhibitor and the inhibition efficiency (IE%) follows the sequence I > II > III > IV. The percentage inhibition efficiency was found to increase with increasing concentration of inhibitors and decreases with increasing temperature of the medium. The addition of KI, KSCN, and KBr to cyanoacetohydrazide derivatives enhanced the inhibition efficiency due to synergistic effect. The effect of temperature on C-steel corrosion in 2 M HCl and with the addition of 11 × 10−6 M of investigated compounds in the temperature range 30°–50°C was studied. Some thermodynamic functions were computed and discussed. The inhibitors are adsorbed on the carbon steel surface according to Temkins adsorption isotherm. Polarization data suggested that the additives used act as mixed-type inhibitors. It was found that the cyanoacetohydrazide derivatives provide good protection to carbon steel against pitting corrosion in chloride-containing solutions.

CORROSION INHIBITION AND ADSORPTION BEHAVIOR OF SOME AZO DYE DERIVATIVES ON CARBON STEEL IN ACIDIC MEDIUM: SYNERGISTIC EFFECT OF HALIDE IONS

Corrosion inhibition of carbon steel in HCl by azo dye derivatives (ADD) was investigated using chemical and electrochemical techniques. Results obtained indicate that ADD inhibited the corrosion of carbon steel in the acid medium. Inhibition efficiency increases with increase in ADD concentration and is synergistically enhanced on addition of iodide and bromide ions. By fitting the obtained experimental data with the Langmuir adsorption model and the Arrhenius equation, some thermodynamic and kinetic parameters for the corrosion process were estimated, and the values support the results obtained. Some quantum chemical parameters and the Mulliken charge densities for ADD were calculated by the MNDO semi-empirical method to provide further insight into the mechanism of inhibition of the corrosion process.

LOW MOLECULAR WEIGHT STRAIGHT-CHAIN DIAMINES AS CORROSION INHIBITORS FOR SS TYPE 304 IN HCL SOLUTION

The effect of some low molecular weight straight-chain diamines to inhibit the corrosion of SS type 304 in 1 M HCl solution is examined by weight loss and galvanostatic polarization techniques. The inhibition efficiency increases with increasing the number of carbon atoms in the chain up to 8 carbons, but at higher than 8 carbon atoms (12 carbons) it decreases again. These diamine compounds act as mixed-type inhibitors, but the cathode is more polarized than the anode when an external current was applied. The corrosion rate in the presence of the investigated diamine compounds was found to increase with increasing the temperature and decrease with increasing the concentration of these compounds. Activation parameters for the corrosion of SS in 1 M HCl were calculated and showed that corrosion was much reduced in the presence of inhibitors. The adsorption of these compounds on SS from 1 M HCl solution obeys the Langmuir adsorption isotherm. The synergistic effect of KI on the inhibitive efficiency of the investigated diamine compounds was also studied.

Phenazone and aminophenazone as corrosion inhibitors for aluminum in HCl solution

The corrosion behavior of aluminum in 1 M HCl solution in the absence and presence of phenazone and aminophenazone was investigated using weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The results of these techniques show that, the inhibition efficiency of these compounds depends on their concentration and chemical structure. The inhibitive action of these compounds was discussed in terms of blocking the electrode surface by adsorption of the molecules through the active centers contained in their structure. The adsorption process was found to obey Temkin isotherm model. The effect of temperature on the rate of corrosion in the absence and presence of these compounds was also, studied. Some activated thermodynamic parameters were computed and discussed. Potentiodynamic polarization data indicated that these compounds act as cathodic type inhibitors. From impedance data it is found that the corrosion of aluminum is controlled by charge transfer process at all concentrations of inhibitors. Quantum chemical parameters were constructed in order to characterize the inhibition performance of the tested molecules.

Some Schiff base compounds as inhibitors for corrosion of carbon steel in acidic media

The corrosion behavior of carbon steel in 0.5 M HCl solution in the absence and presence of new five Schiff bases of indole derivatives was investigated using electrochemical impedance spectroscopy (EIS), electrochemical frequency modulation (EFM) and potentiodynamic polarization techniques. All the experimental results show that these Schiff bases have excellent corrosion inhibition performance. The polarization curves show that these compounds act as mixed type inhibitors. The adsorption of these Schiff bases on carbon steel surface is consistent with Langmuir adsorption isotherm. The effect of temperature on the rate of corrosion in the absence and presence of these compounds were also studied. Some thermodynamic functions were computed and discussed. The results obtained by the three different electrochemical techniques were in good agreement.

Influence of N-thiazolyl-2-cyanoacetamide derivatives on the corrosion of aluminum in 0.01 M sodium hydroxide

The effect of N-thiazolyl-2-cyanoacetamide derivatives on the corrosion of aluminum in 0.01N sodium hydroxide has been studied using weight-loss and glvanostatic polarization techniques. The inhibition efficiency was found to increase with increasing the concentration of inhibitor and with decreasing temperature. The inhibition process was explained in terms of its adsorption on the aluminum surface The adsorption is obeyed Frumkin isotherm. The addition of Ba2+, Sr2+, Ca2+ and Mg2+ ions to N-thiazolyl-2-cyanoacetamide derivatives enhanced the inhibition efficiency due to synergistic effect. Polarization data suggested that the additives used as mixed type inhibitors. Some activated thermodynamic parameters were calculated and explained.

Adsorption and inhibitive properties of Phoenix dactylifera L. Extract as a green inhibitor for aluminum and aluminum-silicon alloy in HCl

The inhibition efficiency of alcoholic extract of Phoenix dactylifera plant on aluminum and aluminumsilicon in 0.5 M hydrochloric acid solution have been evaluated by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM). Values of inhibition efficiency obtained are dependent upon the plant extract concentration and temperature. Generally, inhibition was found to increase with increasing the inhibitor concentration, but decreased with increasing the temperature. The effect of temperature on the corrosion behavior of Al and Al-Si alloy in 0.5M HCl with and without addition of plant extract was studied in the temperature range 20–60°C. Thermodynamic functions of dissolution processes were calculated from experimental EFM data and the interpretation of the results are given. Physical adsorption mechanism has been proposed for the inhibition and Temkin adsorption isotherm was obeyed for Al and Al-Si alloy.