Fouad Taha

Corrosion Inhibition of Mild Steel in Acidic Medium using 2-amino Thiophenoland 2-Cyanomethyl Benzothiazole

The corrosion inhibition characteristics of 2-amino thiophenol (ATP) and 2-cyanomethyl benzothiazole (CNMBT) on two types of steel in 1m HCl medium were investigated at different temperatures (25, 30, 35, 40 and 50°C). The pitting corrosion behaviour for the same system was studied using a potentiodynamic technique. The pitting corrosion resistance of steel samples increased with increase in concentration of the ATP and CNMBT. Some samples were examined by scanning electron microscopy. The effects of the inhibitors on the general corrosion of the two samples were investigated by using gravimetric and galvanostatic polarization techniques. The inhibition efficiencies increased with increase their concentration but decreased with increase in temperature. Free energies of activation, enthalpies and entropies for the inhibition processes were determined from rate constant data measured and different temperatures at different concentrations of ATP and CNMBT. Results were compared with fits obtained from the application of the Langmuir isotherm. Results were correlated to the chemical structure of the inhibitors. The inhibition efficiency of CNMBT is higher than that of ATP.

Inhibition of chloride localized corrosion of mild steel by PO43-, CrO42-, MoO42-, and NO2- anions

The effect of phosphate (PO43−), chromate (CrO42−), molybedate (MoO42−) and nitrite (NO2−) ions on the pitting corrosion of steel in 0.1 M NaCl solution has been studied using potentiodynamic polarization and SEM techniques. The addition of increasing concentrations of PO43−, CrO42−, MoO42− and NO2− anions causes a shift of the pitting potential (Epit) in the positive direction, indicating the inhibitive effect of the added anions on the pitting attack. The adsorption characteristics of these anions on the steel surface play a significant role in the inhibition processes. The PO43−anion has a strong inhibitive effect of chloride pitting corrosion. The effect of different inorganic anions on the pitting corrosion of steel samples I and II (with different composition) was also studied in 0.1 M NaCl solution.

On the pitting corrosion of tin by sulphate anion

Abstract The corrosion behaviour of tin in Na 2 SO 4 solutions at concentrations of 0.1–1.0 M and in the pH range 3–11 was investigated by using potentiodynamic and cyclic voltammetry techniques. The voltammograms involve two anodic peaks prior to the initiation of pitting corrosion. The first peak corresponds to the formation of Sn(OH) 2 and/or SnO. The second peak correlates to the formation of Sn(OH) 4 and/or SnO 2 . The pitting initiation can be explained through the adsorption competition between sulphate anions and the passivating species on the passivated electrode surface. The critical pitting potential depends on the sulphate concentration, pH and scan rate. Three cathodic peaks are observed on the negative-going scan, corresponding to the reduction of the dissolved pitting corrosion products, SnO 2 and SnO respectively. Successive cycling has no significant influence on the pitting potential, but leads to a progressive decrease in the heights of the anodic peaks as a result of incomplete reduction during the cathodic sweeping.

Effect of Cationic and Anionic Surfactants on the Electrokinetic Potentials of Cassiterite and Quartz in the Presence of Polyvalent Cations

The effect of different polyvalent electrolytes (FeCl3, AlCl3, LaCl3, CeCl3 and ThCl4) on the adsorption of different surfactants (primary amine hydrochloride, sodium oleate, sodium dodecyl sulphate and phenyl disodium orthophosphate) on cassiterite and quartz particles has been studied using microelectrophoresis. The zeta potentials of the oxides and their isoelectric points were determined as a function of pH in the presence of constant concentrations of both surfactants and electrolytes. The mechanism of adsorption of surfactants on cassiterite and quartz surfaces modified by salt cations is discussed. In general, in the presence of the above-mentioned salts, the zeta potentials and the isoelectric points (IEPs) of the oxides are considerably changed on addition of different surfactants.

Non-aqueous olive oil-in-glycerin (o/o) Pickering emulsions: Preparation, characterization and in vitro aspirin release

ABSTRACT Non-aqueous olive oil-in-glycerin Pickering emulsions are successfully prepared and stabilized solely by hydrophobic silica nanoparticles possessing 50% silanol groups. Various aspects related to the preparation and physicochemical stability of such promising emulsions are investigated. The resulted emulsions exhibited excellent stability against coalescence for above one year. The apparent viscosity of the olive oil-in-glycerin emulsions is explored as a function of silica nanoparticle concentration and drop volume fraction for the first time. The flow behavior of these emulsions followed the non-Newtonian shear-thinning trend. Both simple o/o and multiple o/o/o emulsion types can be stabilized by one and the same silica nanoparticles during the catastrophic phase inversion, occurred at drop volume fraction between 0.4–0.5. Our findings are correlated with the widely accepted surfactant or solid-stabilized systems. The potential use of such unique emulsions as drug delivery vehicles is studied. GRAPHICAL ABSTRACT