Anodic behaviour of tin in maleic acid solution and the effect of some inorganic inhibitors

The passivity breakdown of zinc antimony alloy as an anode in the alkaline batteries

Zn is utilized as an anode in alkaline batteries because of its propensity to produce a passive colloidal layer on its surface. Then the surface should be reactivated in the passive region. Therefore, the passive state on the surface can be significantly hindered by utilizing a tiny percentage of Sb alloyed with Zn. Accordingly, the effect of minor Sb alloying with Zn on the performance of anodic dissolution and passivation in concentrated alkaline media (6 M KOH, which is used in the batteries) was studied using potentiodynamic and potentiostatic techniques. Besides, the passive layers formed at various anodic potentials were characterized utilizing scanning electron microscopy (SEM) and X-ray diffraction (XRD). The data of potentiodynamic measurements exhibited the active-passive transition curve of all studied specimens. All obtained results revealed that passivation is gradually hindered with increasing Sb content in the alloy, and less passivity was obtained at 1% Sb. Along this, a dramatic rise in current density at a particular positive potential (+ 2.0 V vs. SCE) to markedly higher values only of the electrodes containing Sb is observed.

Dissolution of Metals in Different Bromide-Based Systems: Electrochemical Measurements and Spectroscopic Investigations

The dissolution of the main metals (Cu, Zn, Sn, Pb and Fe) found in waste printed circuit boards (WPCBs) was investigated by electrochemical corrosion measurements (potentiodynamic polarization and electrochemical impedance spectroscopy (EIS)) in different bromide-based systems that could be used as lixiviants in hydrometallurgical route of metals recovery. The analysis of the corrosion products was carried out by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements. All measurements showed that the addition of bromine in the electrolyte favors to great extents the dissolution process of all studied metals as compared to bromine-free electrolytes. In the investigated experimental conditions, the highest dissolution rates of the metals were obtained in acidic KBr solution containing 0.01 mol/L bromine and they decreased in the following order: Zn >> Sn > Pb > Fe > Cu. The XRD and XPS chemical assessment allowed the identification of the dissolution products formed on the metallic surfaces after exposure to the electrolytes. They consisted mainly of oxides in the case of Cu, Zn, Sn and Fe, while the presence of PbBr₂ was also noticed on the lead surface. Based on the results of EIS and surface investigations, several models explaining the corrosion behavior of the metals were proposed and discussed. The obtained results demonstrate that all studied metals could be successfully leached using brominated solutions, providing a viable alternative for the selective and efficient recovery of the base metals from WPCBs through a multi-step hydrometallurgical processing route.

Role of Indium Alloying with Lead as a Means to Reduce the Passivation Phenomena in Lead/Acid Batteries

The influence of indium content on the anodic behaviour of Pb-In alloys in 4 M H2SO4solution is investigated by potentiodynamic, potentiostatic, chronopotentiometric, and cyclic voltammetric techniques. The composition and microstructure of the corrosion layer on Pb-In alloys are characterized by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy analysis (EDX), and scanning electron microscopy (SEM). The potentiodynamic and chronopotentiometric curves show that the anodic behavior of all investigated electrodes exhibits active/passive transition. The active dissolution (except for alloy I) and passive currents increase with increasing both In content and temperature. This indicates that the conductivity of the anodic film on Pb-In alloy is enhanced. This study exhibits that indium catalyses the oxidation of Pb (II) to Pb (IV) and facilitates the formation of a more highly conductive corrosion layer on lead. Alloy I (0.5% In) exhibits that the corrosion rate is lower, while the passive current is higher than that of Pb. XRD, EDX, and SEM results reveal that the formation of both PbSO4and PbO on the surface decreases gradually with increasing In level in the alloy and completely disappear at higher In content (15% In). Therefore, recharge of the battery will be improved due to indium addition to Pb.