Ahlam M. Fathi

Effect of Nickel Content on the Corrosion and Passivation of Copper-Nickel Alloys in Sodium Sulfate Solutions

Abstract The effect of Ni content on the corrosion and passivation behaviors of copper-nickel alloys with different Cu to Ni ratios was investigated in neutral sulfate solutions. The influence of working conditions (e.g., immersion time, sulfate ions concentration, and temperature) on the electrochemical behavior of the different alloys was also studied. In this respect, conventional electrochemical methods like open-circuit potential (OCP) measurements, polarization techniques, and electrochemical impedance spectroscopy (EIS) were used. It was found that the initial corrosion resistance is relatively low for alloys with high nickel content. An increase in the nickel content and long immersion time in the neutral sulfate solution increases the corrosion resistance of the alloy and improves its stability. The stability of the alloy was considered to be due to the formation of a stable passive film on its surface. The impedance data were fitted to theoretical data obtained according to an equivalent circuit...

Electrocatalytic Oxygen Evolution on Nanoscale Crednerite (CuMnO2) Composite Electrode

Abstract In this study, nanoscale crednerite (CuMnO2) was prepared in the system xCuO–(70–x)MnO–30SiO2 , where x has values 10, 15, 20, 25 and 30, via melting quenching glass-ceramic technique. The electrocatalytic activity of the oxygen evolution reaction (OER) on CuMnO2 deposits has been studied in 1.0 M KOH (25 ℃) by means of cyclic voltammetry, linear sweep voltammetry, chronoamperometric and electrochemical impedance techniques. The study has shown that the catalytic activity had increased with the increase of Cu content in the electrode composition, where the optimum improvement in the apparent electrode catalytic activity was obtained at the M30 electrode (with x = 30). At E = 0.6 V versus Ag/AgCl, the apparent oxygen evolution current density observed at the M30 electrode is 4 times greater than that observed with M10 (x = 10). The order of the OER with respect to OH– concentration measured at low and high potentials is ∼ 1.0 and the roughness of the electrodes was decreased with the increase of the Cu content.

Influence of Ni–Cu–P Deposits on the Surface Characteristics of Anodized Al, Al2014 and Al7075

Abstract Nickel-copper-phosphorous layers were electro-less deposited on the surface of anodized aluminum and aluminum alloys. The electrochemical behavior of the improved surface was investigated in 0.5 M Na2SO4. The corrosion resistance of the modified alloys surface is ten folds that measured on the anodized materials. The surface morphology was examined by scanning electron microscopy, SCE, and the deposit composition was subjected to x-ray energy dispersive analysis, EDAX. The experimental impedance data were fitted to theoretical data according to a proposed equivalent circuit model. The results show that the Ni–Cu–P layer was deposited homogeneously on the anodized Al surface but on the anodized-alloy surface the layer had a defective nature.