J.P. Hilger

Passivation and corrosion phenomena on lead-calcium-tin alloys of lead/acid battery positive electrodes

Abstract The corrosion behaviour of lead-calcium-tin alloys has been examined at two anodization potentials that correspond, respectively, to overcharge and to passivation by PbO conditions. The role of tin on the passivation phenomenon is examined in detail, while the evolution of hardening and microstructure is followed on the same samples, namely, grids (expanded and gravity cast) with different tin levels and strips, manufactured from primary or secondary lead.

Improved lead alloys for lead/acid positive grids in electric-vehicle applications

Abstract Currently, the excessive weight of the positive grid is a limiting factor to the increase of the specific energy of the lead/acid battery. With present alloys, a thickness of a few millimeters is a pre-requisite in the processing of a positive grid which is submitted to heavy corrosion during the charge and deep-discharge cycles usually encountered with electric vehicles. The search for a lighter battery approaching the ALABCs goal of 50 Wh kg −1 therefore requires the development of a new set of alloys that are able to withstand mechanical stress and corrosion experienced by a positive grid during the service life of an electric-vehicle battery. The work reported here shows that tin addition (to a level of 1.2 wt.%) or combined tin (to a level of 0.6 wt.%) and silver (to a level of 0.05 wt.%) additions increase considerably both the mechanical properties and the corrosion resistance of a Pb-0.08wt.%Ca-0.013wt.%Al alloy. Gravity casting trials reveal that the tin-rich alloy (1.2 wt.%) and the silver-rich alloy (0.05 wt.%) could be used directly in the industrial processing of batteries that use gel technology. Information is also given on the performances of these batteries when submitted to the international TC69 cycling test, as well as indications of the minimum grid thickness that could be achieved with these alloys without sacrificing battery cycle life.

New aspect of the solid phase equilibria in the ternary PbSnCa system for xCa≤25 at.%

Abstract New crystallographic data prove that CaPb 3 and Sn 3 CaL1 2 compounds belong to the same single-phase Ca(Pb,Sn) 3 domain in the ternary PbSnCa equilibrium phase diagram. A tentative calculation of this diagram shows that about 2 wt.% Sn, introduced in the α-Pb matrix, allows a decrease in the solubility of Ca at 400 K from 10 t-2 to 10 −7 wt.%. Simultaneously, the L1 2 compound, in equilibrium with the α-Pb matrix, crosses rapidly the x Ca =0.25 line, continuously from the PbCa border to near the SnCa border, when increasing the Sn content in the α matrix from zero to 8 wt% Sn at 400 K. A very large triangle formed by the three phases α-Pb (8 wt% Sn), β-Sn (1.7 wt.% Pb), Ca 25 Pb 5 Sn 70 L1 2 appears in this diagram at 400 K. This triangle provides a ternary eutectic, calculated at 424 K. This calculation brings to light some reasons for the process transition for the hardening of PbCa grid-battery alloys, from discontinuous to continuous, when increasing the tin content.

Hardening process in ternary lead-antimony-tin alloys for battery grids

Abstract It is known that lead-antimony alloys are very well hardened by continuous precipitation, whereas lead-tin alloys present a discontinuous precipitation with a weak hardening effect. In these binary alloys, there is precipitation of either antimony or tin. In ternary alloys, the compound SbSn can also precipitate. This study is focused on the type of precipitation, the nature and the morphology of the precipitated phases, and the intensity of hardening in ternary PbSbSn alloys in relation to the composition of the alloys and the ternary diagram. To simulate the different processes of grid production, four states are studied, namely, as-cast product, rehomogenized, cold worked, cold worked and rehomogenized. The alloys contain up to 2.5 wt.% Sb and 2.5 wt.% Sn.

Piles de mesure àélectrolyte solide utilisant une ou deux électrodes ponctuelles en régime transitoire: I. Application à la mesure des enthalpies libres standards d'oxydation des métaux purs

The point electrode is a metal point touching a solid electrolyte (calcia stabilized zirconia), in an atmosphere with a controlled oxygen partial pressure. The system is equipped with an oxygen pump mounted before the cell, which is electronically controlled and attains 10−20 atm O2. The potential-time curves of the depolarisation of the point electrode permits a dynamic study of the oxidation of the metal, or of the reduction of its oxide. The point electrode has a very small inertia; the steps on the potential-time curves, even when strongly inclined, can be used to determine the standard free enthalpies of oxidation of pure metals. The measuring cell can be equipped, either with one point electrode associated with a reference electrode at a stable potential, or with two point electrodes placed side by side without any separation. The results obtained for the systems CuCu2O and CoCoO serve as applications.

How to decrease overaging in Pb–Ca–Sn alloys?

Abstract It is known that lead–calcium–tin alloys are very well hardened by continuous precipitation since 20°C. But an overaging involving a decrease of the mechanical properties appears afterwards. It is proved in this study that with an adapted combination of the composition of the Pb–Ca–Sn alloys and a specific heat treatment it is possible to reach a hardness of 25 to 30 Vickers with a complete precipitation of (Pb1−xSnx)3Ca and to suppress practically any overaging in as-cast or rolled specimens.

The Effect of the Lead Alloy Hardening Process in Electric Vehicle Storage Batteries on Corrosion Resistance

This study focuses on two types of precipitation in both ternary Pb-Ca-Sn alloys (up to 5 wt % Sn) and quaternary Pb-Ca-Sn-Ag/In alloys (up to 0.5 wt % Ag/In) as well as on the nature and morphology of the precipitated phases and the hardening intensity. Several structural states are studied including gravity cast for grids, rolled, and as-cast for strips. The corrosion behavior at the anodization potential of 1.5 V under overcharged battery conditions is determined in relation to both alloy composition and type of precipitation. A correlation between the mechanical properties of the alloys and their electrochemical behavior is clearly established. Thus, the Pb-Ca-Sn alloys with high tin contents (1-2 wt %) as well as the quaternary Pb-Ca-Sn-Ag alloys, which harden following a continuous transformation, present a better corrosion resistance in overcharge conditions.