Masami Taguchi

Electrochemical characteristics of Pb–Sb alloys in sulfuric acid solutions

Abstract Lead–antimony alloys with a wide range of Sb contents, pure Pb and pure Sb were subjected to sulfuric acid solutions to elucidate their electrochemical characteristics by cyclic voltammetry and corrosion potential measurements. A corrosion test with a Pb/Sb galvanic couple was also done. For Pb-rich α-phase alloys ( 0.3 wt.% Sb) their behavior was quite different from those of α-phase alloys; (i) dissolution current of Sb was proportional to Sb contents; (ii) hydrogen overvoltage was decreased remarkably with increasing the Sb contents; (iii) the corrosion potential shifted and approached that of pure Sb with time. It is confirmed that the electrochemical behavior of Pb–Sb alloys is related to the electrochemical property of the individual phase involved in the internal galvanic couples formed.

Creep Behavior of Powder-Rolled Pb-Base Alloy as Grid Material in Lead-Acid Battery

For extending the life of a lead-acid battery, the control of the creep of a Pb-base alloy as the grid material is of great importance. In this study, Pb-1.50 mass%Sn alloys were produced by two different processes, namely the cast-rolling process and the powder-rolling one, in order to study the influence of the crystallographic structure on the creep behavior of the Pb-base alloy. The structure produced by the cast-rolling, which is the commonly used process in the lead-acid battery industry, consists of relatively large grains. On the other hand, the powder-rolling is a new process for the preparation of the grid material, which uses air-atomized powders as the raw materials. The mean size of crystal grains of the powder-rolled Pb-base alloy is extremely small in comparison with that of the cast-rolled one. The tensile strength and the Vickers hardness of a Pb-1.50 mass%Sn powder-rolled alloy are 23 MPa and ca. Hv 9.0, respectively. Although these values are twice larger than those of a Pb-1.50 mass%Sn cast-rolled alloy, they are lower than the values of the Pb-base alloy in common use of the VRLA battery, or a Pb-0.08 mass%Ca-1.20 mass%Sn cast-rolled alloy. However, the corrosion creep test showed that the steady creep rate of a Pb-1.50 mass%Sn powder-rolled alloy was extremely smaller than those of all the Pb-base cast-rolled alloys. This finding suggests that the powder rolling process is very effective to improve the creep resistance of a Pb-base alloy as a grid material in a lead-acid battery. It can be also presumed that fine grain size in the powder-rolled alloy of Pb-1.50 mass%Sn function as an obstacle to the movement of dislocation, resulting in remarkably the suppression of the creep rate.

Effect of anion concentration on anodic dissolution of iron and titanium.

To evaluate effect of hydroxide and chloride ions on dissolution of iron and titanium, anodic polarization behaviour has been investigated in both xNaCl+yHCI and xHCIO4+yHCI solutions (x+y=4.50kmol·m-3). The anodic dissolution of iron in low [H+] -concentrated chloride and highly acidic-low [Cl-] solutions can be interpreted by the hydroxide mechanism. On the other hand, it is explained by the chloride mechanism for highly acidic-high [Cl-] and high [H+] -concentrated chloride solutions. The amount of adsorbed intermediate, ΔQ measured using a channel flow double electrode method increases with decreasing the concentration of [H+] in low [H+] -concentrated chloride solutions and increasing that of [Cl-] in highly acidic-high [Cl-] solutions. X-ray photoelectron spectroscopy shows that the hydroxide mechanism brings. γ-FeOOH and Fe2O3 as the final reaction products, while the products by the chloride mechanism are FeCl2 and FeCl3. The anodic dissolution of titanium is characterized that the hydroxide mechanism does not occur and hydroxide ions act as an inhibitor to the chloride mechanism.