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Article
Publication date: 1 April 2001

E.E. Abd El Aal

Cyclic voltametry and potentiodynamic single sweep techniques are used to study the electrochemical behaviour of lead in Na2CO3 solutions containing various concentrations…

Abstract

Cyclic voltametry and potentiodynamic single sweep techniques are used to study the electrochemical behaviour of lead in Na2CO3 solutions containing various concentrations of ClO4 as aggressive anion. The effects of different concentrations, in terms of destruction of passivity and initiation of pitting corrosion, were monitored with reference to the change in integrated anodic charge. It was found that Δqa (taken as a measure of the extent of pitting) varies linearly with log CClO4. The pitting corrosion potential, Epitting, varies with log CClO4 according to sigmoidal curves. These curves are explained on the basis of formation of passive, active and continuously propagating pits. Additions of aliphatic amines shift the pitting corrosion potential, Epitting, into the noble (positive) direction, indicating the inhibition action of the added amines on the pitting attack. Epitting varies with the logarithm of the inhibitor concentration according to: Epitting = a + b log Cinh. The inhibition of pitting corrosion by the aliphatic amines is assumed to be due to either competitive adsorption between the CO32– with ClO4 anions, and/or the chemisorption of the amine on the metal with the formation of a metal‐nitrogen coordination bond. The efficiency of these compounds as pitting corrosion inhibitors increases with the increase in the chain length of the alkyl group.

Details

Anti-Corrosion Methods and Materials, vol. 48 no. 2
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 1 April 2007

Abd El Hakeem Abd El Naby and M.F. Abd El Kareem

The peristaltic motion for Carreau fluid by means of an infinite train of sinusoidal waves traveling along the walls of a circular cylindrical flexible tube is…

Abstract

The peristaltic motion for Carreau fluid by means of an infinite train of sinusoidal waves traveling along the walls of a circular cylindrical flexible tube is investigated. The fluid is subjected to a constant transverse magnetic field. A perturbation solution is obtained for the case in which Weissenberg number is small. The effects of Hartmann number, Weissenberg number, power‐law index and amplitude ratio on the pressure rise and the friction force are discussed. The trapping limit and the trapping occurrence region at the centerline decrease by increasing Hartmann number but they are independent approximately of Weissenberg number and power‐law index.

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Multidiscipline Modeling in Materials and Structures, vol. 3 no. 4
Type: Research Article
ISSN: 1573-6105

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Article
Publication date: 1 April 1994

E.E. Abd El Aal, A. Abd El Aal and S.M. Abd El Haleem

The effect of the addition of aggressive salts such as LiCl, NaCl, KCl, RbCl and MgCl2 on the steady‐state potential of a Zn electrode previously equilibrated in a…

Abstract

The effect of the addition of aggressive salts such as LiCl, NaCl, KCl, RbCl and MgCl2 on the steady‐state potential of a Zn electrode previously equilibrated in a passivating chromate solution is established. S‐shaped curves are obtained for the variation of the steady‐state potential with the quantity of aggressive salt added. For each inhibitor concentration, Cinh, the addition of aggressive ions up to a certain concentration has no effect on the passivity of Zn. However, higher Cl ion concentration causes destruction of the passive film and initiation of pitting corrosion. Destruction of passivity occurs after an induction period which decreases with the increase in the concentration of the attacking ion and/or the decrease in that of the inhibiting ions. The concentration of aggressive ion, Cagg, that can be tolerated by a certain concentration of the inhibiting ions, Cinh, is given by the relation : log Cinh =K + n log CCl−, where K and n are constants. The efficiency of these salts in initiating pitting corrosion increases in the order RbCl ≤ MgCl2, ≤ KCl < NaCl < LiCl. The change in the degree of aggressivity of these salts could be attributed either to the incorporation of the cations in the passive film or to their effect on pH.

Details

Anti-Corrosion Methods and Materials, vol. 41 no. 4
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 1 April 2009

A.H. Abd Elnaby and I.I. El Shamy

In order to determined the characteristics of peristaltic transport of the Newtonian fluid with variable viscosity through a cylindrical tube having walls that are…

Abstract

In order to determined the characteristics of peristaltic transport of the Newtonian fluid with variable viscosity through a cylindrical tube having walls that are transversely displaced by an in finite, harmonic traveling wave of large wavelength and negligibly small Reynolds number was analyzed in the presence of magnetic field directed with an angle π A perturbation method of solution is thought. The viscosity parameter a <<1 is chosen as a perturbation parameter. It serves as a model for the study of flow of chyme through small intestines. The governing equations are developed up to first‐order in the viscosity parameter (a). In case of the first‐order system, simpling a complicated group of products of Bessel functions by approximating polynomial. The results show that, the increasing of magnetic field increases the pressure rise. Also, the pressure rise at normal magnetic field (ω=π/2) is greater than the pressure rise at inclined magnetic field (O<ω>π/2). In addition, the pressure rise increases as the viscosity parameter decreases at certain values of flow rate. Comparisons with other studies are given.

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Multidiscipline Modeling in Materials and Structures, vol. 5 no. 4
Type: Research Article
ISSN: 1573-6105

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Article
Publication date: 1 December 1991

S. Abd El Wanees, E.E. Abd El Aal and A. Abd El Aal

The potentiodynamic anodic polarization curves for the lead electrode were obtained in 0.1 mol L‐1 KOH solution in the absence and presence of C103‐ or C104‐ as aggressive…

Abstract

The potentiodynamic anodic polarization curves for the lead electrode were obtained in 0.1 mol L‐1 KOH solution in the absence and presence of C103‐ or C104‐ as aggressive ions at different concentrations. Lower concentrations of these ions have no significant influence on the passive film, while higher concentrations raise the active dissolution current density, and cause destruction of passivity and initiation of pitting corrosion. The critical pitting corrosion potential varies with the concentration of the aggressive ions according to sigmoidal curves. These curves were explained on the basis of the formation of passivitable, active and continuously propagagting pits depending on the range of the aggressive ion concentration. Additions of increasing concentrations of chromate, phosphate, sulphate and carbonate ions cause a shift of the critical pitting potential in the noble direction accounting for increase resistance to pitting attack (inhibition). The pitting corrosion potential varies with the concentration of the inhibitive ions, in the presence of a constant concentration of the aggressive ions, according to curves of sigmoidal shape. From these curves one can determine the minimum concentration of the inhibitive ions necessary for inhibition of pitting corrosion to occur.

Details

Anti-Corrosion Methods and Materials, vol. 38 no. 12
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 1 October 1999

E.E. Abd El Aal

The electrochemical behaviour of zinc in different concentrations of Na2SO4 (pH = 6.0) was investigated using the potentiodynamic anodic polarization single sweep and…

Abstract

The electrochemical behaviour of zinc in different concentrations of Na2SO4 (pH = 6.0) was investigated using the potentiodynamic anodic polarization single sweep and cyclic voltammogram techniques. The anodic portion is characterized by one distinct peak corresponding to Zn(OH)2 or ZnO. This is followed by a passive region up to a certain potential; the passive current suddenly rises steeply without any sign of oxygen evolution. This denotes the breakdown of the passive film and initiation of pitting corrosion. It was found that the breakdown potential depends on the sulphate concentration, type of aeration, scan rate, solution temperature and pH. The pitting initiation may be explained through the adsorption of SO42– anion on the oxide film formed. This decreases the repair efficiency and causes further metal dissolution. From the cyclic voltammogram of zinc in different concentrations of Na2SO4, it was found that the change in the integrated anodic charge, Δqa, which is taken as a measure of the extent of pitting, varies linearly with concentration of SO42– anion.

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Anti-Corrosion Methods and Materials, vol. 46 no. 5
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 1 February 1990

A.A. Abd El‐Hakim, M.A. Abd El‐Ghaffar, M.M. Abd El‐Malek and E.A.M. Youssef

Results and discussion Adsorption isotherms of stearic acid on the surface of manganese ore samples:

Abstract

Results and discussion Adsorption isotherms of stearic acid on the surface of manganese ore samples:

Details

Anti-Corrosion Methods and Materials, vol. 37 no. 2
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 11 February 2019

Nobl Foad El Boraei, Sayed S. Abd El Rehim and Hamdy H. Hassan

The purpose of this paper is to study the electrochemical behavior of Sn electrode in Na2B2O7 solutions in the absence and presence of NaNO3 as a pitting corrosion agent.

Abstract

Purpose

The purpose of this paper is to study the electrochemical behavior of Sn electrode in Na2B2O7 solutions in the absence and presence of NaNO3 as a pitting corrosion agent.

Design/methodology/approach

The electrochemical behavior of Sn electrode was studied by using cyclic voltammetry and potentiodynamic polarization measurements and complemented with scanning electron microscopy examinations.

Findings

This paper shows that in the absence of NO3 − ions, the anodic polarization of Sn electrode exhibits active/passive transition. Addition of various concentrations of NO3 − anions to the borate solution enhances active anodic dissolution and tends to break down the passive oxide film at a certain pitting potential. The pitting potential, and hence the pitting corrosion resistance, decreases with increasing NO3-ion concentration and temperature but increases with scan rate and repetitive cycling. Addition of CrO42−, WO42− or MoO42− oxyanions to the borate nitrate solution inhibits the pitting corrosion of Sn.

Originality/value

This is the first study that shows the effect of NO3 − ion as a pitting corrosion agent.

Details

Anti-Corrosion Methods and Materials, vol. 66 no. 3
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 1 June 1996

M.A. Abd El‐Ghaffar, E.A.M. Youssef, M.M.H. Abo‐Shosa and N.A. Ibrahim

Modifies short and medium alkyd resins using perfluori‐nated urethane toluene isocyanate (PFUTI), and incorporates the modified resins in a set of paint formulations…

Abstract

Modifies short and medium alkyd resins using perfluori‐nated urethane toluene isocyanate (PFUTI), and incorporates the modified resins in a set of paint formulations containing different ratios of zinc phosphate as an inhibitive pigment. Achieves promising results and illustrates corrosion‐protective properties in various paint formulations and also a paint formulation free of the inhibitive pigment. Shows enhancement of the corrosion protection efficiencies by the improvement in the hydrophobicity of alkyd resin modified with PFUTI. In view of these results, minimizes or neglects the most expensive inhibitive pigments from an economical standpoint.

Details

Pigment & Resin Technology, vol. 25 no. 6
Type: Research Article
ISSN: 0369-9420

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Article
Publication date: 1 January 1990

A.A. Abd El‐Hakim, M.A. Abd El‐Ghaffar, M.M. Abd El‐Malek and E.A.M. Youssef

The adsorption of stearic acid molecules onto the surface of the Egyptian manganese ore (high and medium grades, H.G. & M.G.) was followed by adsorption isotherm…

Abstract

The adsorption of stearic acid molecules onto the surface of the Egyptian manganese ore (high and medium grades, H.G. & M.G.) was followed by adsorption isotherm determination and the sedimentation properties of the ore in apolar medium. It was found that the sedimentation properties depend on the adsorbed amount in the isotherm, the most stable dispersion for the ore in the organic medium was detected at monolayer surface coverage of stearic acid molecules on the surface of the ore.

Details

Anti-Corrosion Methods and Materials, vol. 37 no. 1
Type: Research Article
ISSN: 0003-5599

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