H. Nady

Electrochemical behavior and stability of Cu-Al-Ni alloys in NaOH solutions”

Abstract The electrochemical behavior of copper-aluminum-nickel alloy with different Ni content in sodium hydroxide solutions was investigated. The alloys are usually used as tubes and reservoirs in basic solutions for the production of salts from marine solutions. The role of the Ni-content on the corrosion resistance of the alloy was evaluated. Different electrochemical methods were used. The increase of the nickel content in the alloy and increased immersion time in the solution improve the alloy stability due to the formation of a stable passive film. The experimental impedance data were fitted to theoretical data. The results of these experiments are discussed in reference to potential-pH (Pourbaix) diagrams. Surface morphology and barrier film constituents were examined by SEM.

Beneficial Effects of Zn, Al and Ni Addition on the Stability of Some Cu-Ternary Alloys in Acidic Solutions

Copper-based alloys are important materials for many industrial applications but suffer from accelerated corrosion in acidic solutions. In the present work, we investigated the synergistic effects of Al, Ni and Zn as alloying elements on the electrochemical behavior of some Cu-ternary alloys in acidic solution of pH 2. The stability of some Cu-ternary alloys (Cu–10Al–10Zn, Cu–10Al–10Ni and Cu–10Ni–10Zn) in acidic solution (pH 2) was investigated using open-circuit potential measurements, polarization techniques and electrochemical impedance spectroscopy. The electrochemical behavior of the investigated Cu alloys was dependent on the alloying elements. The results showed that the Cu–10Al–10Zn alloy is more stable than the other two studied alloys. The alloy surface was covered by a barrier layer protecting it from acidic corrosion. The thickness and resistance of the barrier film formed on the Cu–10Al–10Zn alloy increase with the increase in the immersion time. The corrosion process mechanism and the formation of barrier film were explained. The incorporation of Zn ions in the Cu2O barrier film leads to its stabilization, and the stability is enhanced by the presence of Al metal. Based on the analysis presented in the paper, it is concluded that the Cu–10Al–10Zn alloy is highly promising for application in the in acidic environments.

Comparison of Electrochemical Behavior of Cu-10Ni-10Zn Alloy and Cu in Aqueous Solutions

Abstract The electrochemical behavior of Cu-10Ni-10Zn alloy and Cu was investigated in acidic, neutral and basic solutions. The effect of chloride ions in neutral solutions was also studied. Conventional electrochemical techniques and electrochemical impedance spectroscopy were used. The corrosion rate of these materials in acidic solutions is relatively high compared to that in neutral or basic solutions. The open-circuit potential of the alloy is nearly the same as that of pure copper in the different media, indicating that the processes which occur on the alloy surface are mainly governed by copper dissolution. In chloride solutions the rate of Cu corrosion is remarkably high. In the alloy, the copper dissolution was suppressed by the presence of nickel and zinc, due to the formation of complex oxide layers. The impedance data were fitted to equivalent circuit models that explain the different electrochemical processes occurring at the electrode/electrolyte interface. SEM and EDAX have shown that the alloy surface is enriched with Ni. In neutral solutions the chloride ions are penetrating the metallic surface.