Evaluación de la corrosión de una aleación Pb-Ca-Sn por medio de técnicas electroquímicas

Abstract

In this paper, the influence of increasing temperature on the corrosion rate of Pb-Ca-Sn alloy, the primary component of the negative grid of a starter battery car, was evaluated by electrochemical techniques: RPL, potentiodynamic curves, Tafel and EIS. By optical microscopy, SEM -EDS and XRD, the compounds formed on the grids were characterized during testing. The passive layer formed on the grids used as cathode and anode in lead-acid batteries allows the anchor in grid-PAM interface (Positive Active Material) or NAM (Negative Active Material). A bad process of to form this layer produces the detachment of PAM/NAM, leading to premature failure. The temperature directly affects the kinetics and thermodynamics degradation of the redox reactions taking place in the system grid-PAM/NAM. An increase in temperature causes variations in the chemical composition, favoring the formation of oxides and sulphates mixtures in grid-PAM/NAM interface, its volume and porous structure make it susceptible to failure by tri-axial stress on the interface, producing cracks and detachment of PAM or NAM and reducing the lifetime of the battery. It was found that the Pb-Ca-Sn alloys in 0.5M H2SO4 solution form a multilayer system, verified by the results of EIS and SEM, in which a compact layer of PbO2 and porous layer by PbSO4. Porous layer of PbSO4 was obtained, when the temperature was increased implying greater corrosion kinetics of Pb-Ca-Sn alloy were detected.

Keywords

• lead-acid battery
• negative active material
• corrosion
• electrochemical techniques