Search

This paper reviews the common lead alloys associated with insoluble anodes in different metal deposition operations. Metallographic techniques were used to evaluate microstructures as they relate to physical and mechanical properties. Alloy additions and manufacturing processes are examined as appropriate methods to meet the performance needs of a lead anode.

Lead–antimony alloys used for the positive grids in lead–acid batteries for cycling service have generally used antimony contents of 4.5 wt.% and above. Tubular batteries for cycling service that impart high compression of the active material to the grid surface via gauntlet use alloys with antimony contents as low as 1.5 wt.%. These batteries are generally employed in less-severe cycling service. Value-regulated lead–acid (VRLA) batteries can give good cycling service without lead–antimony in the positive grid, but require a high tin content and high compression. The change in automotive battery positive grid alloys to lead–calcium–tin and the tin contents of VRLA positive grids and straps have dramatically increased the tin content of the recycled grid and strap lead in the USA, Europe, and Australia. The higher tin contents can contaminate the lead used for lead–antimony battery grids and generally must be removed to low levels to meet the specifications. This study describes a low-antimony alloy that contains a substantial amount of tin. The high tin content reduces the rate of corrosion of low-antimony positive grid alloys, improves conductivity, increases the bond between the grid and the active material, and cycles as well as the traditional 5–6 wt.% antimony alloys employed in conventional flat-plate batteries. The alloy is also used as a corrosion-resistant cast-on strap alloy for automotive batteries for high temperature service, as well as for posts, bushings, and connectors for all wet batteries.

In the past several years, there have been many developments in the materials for lead–acid batteries. Silver in grid alloys for high temperature climates in SLI batteries has increased the silver content of the recycled lead stream. Concern about silver and other contaminants in lead for the active material for VRLA batteries led to the initiation of a study by ALABC at CSIRO. The study evaluated the effects of many different impurities on the hydrogen and oxygen evolution currents in float service for flooded and VRLA batteries at different temperatures and potentials. The study results increased the understanding about the effects of various impurities in lead for use in active material, as well as possible performance and life improvements in VRLA batteries. Some elements thought to be detrimental have been found to be beneficial. Studies have now uncovered the effects of the beneficial elements as well as additives to both the positive and negative active material in increasing battery capacity, extending life and improving recharge. Glass separator materials have also been re-examined in light of the impurities study. Old glass compositions may be revived to give improved battery performance via compositional changes to the glass chemistry. This paper reviews these new developments and outline suggestions for improved battery performance based on unique impurities and additives.

The production of vehicles utilizing 36 V battery systems has begun with the introduction of the Toyota Crown. Other vehicles with 36 V batteries are in the near horizon. These vehicles may contain single or dual battery systems. These vehicles will most likely contain valve-regulated lead–acid (VRLA) batteries. The battery systems developed to date utilize significantly more lead than conventional 12 V batteries. This paper will evaluate the different proposed 36 V battery systems and estimate the lead requirements for each of the competing systems. It will also project the penetration of and resultant increased lead usage of these new batteries into the future.

On a weight basis lead is the fifth most used metal in the world. As a metal, lead is prized for properties such as high density, ease of fabrication, chemical stability in air and water, ability to absorb high energy radiation, and for its electrochemistry, especially the reaction with sulfuric acid. The lead–acid storage battery is used worldwide. Lead also forms alloys and compounds. Lead is generally recovered from ores containing 2–6% lead sulfide. After concentration, the sulfide is smelted to metal, refined to remove impurities, and the valuable by-products such as silver and gold recovered. Refining and by-product recovery are achieved by traditional pyrometallurgical and electrolytic methods. These primary production methods are described. Recycling of the lead in scrap lead–acid batteries is steadily increasing and, in the United States, accounts for two-thirds of the lead consumed annually. Secondary production methods are described, including technologies under development to improve recycling capabilities. The principal metals alloyed with lead are antimony, arsenic, calcium, copper, tin, tellurium, and silver. Minor alloying elements are cadmium, bismuth, selenium, indium, aluminum, and strontium. Lead alloys are generally melted and cast into molds to produce useful shapes. The alloys are also rolled, extruded, and forged. The primary use for lead alloys is in the production of battery parts for lead–acid batteries. Smaller but significant uses are ammunition, cable sheathing, sheet for roofing and construction, insoluble anodes, solders, and special low melting point materials. Lead is toxic to the kidney, cardiovascular system, developing red blood cells, peripheral and central nervous systems, testes, and fetus. Exposure to lead may occur from a variety of occupational and nonoccupational sources. Exposure, toxicity, and detection of lead in humans is discussed as is the treatment of lead poisoning. Keywords: lead; ores; smelting; lead emissions; refining; secondary lead; recycling; lead-antimony; lead-calcium; lead-acid batteries; lead-copper; lead-silver; lead-tin; solders; corrosion protection; bearings; sound abatement; radiation shielding; nonoccupational exposure; occupational exposure; toxicity; lead poisoning

During the past several years extremely corrosion-resistant positive grid materials have been developed for lead acid batteries. These alloys consist of a low calcium content, moderate tin content, and additions of silver. Despite the high corrosion resistance these materials present problems in battery manufacturing. The very low calcium contents produce soft grids which harden very slowly and require artificial aging at high temperatures to produce adequate mechanical properties for pasting and subsequent handling. The silver and tin additions yield grids which are very corrosion resistant. The grid, however, must be corroded in the pasting/curing process to permit the paste to adhere to the grids. Battery manufacturers have had to go to great lengths to corrode the grids to provide adequate attachment of the active material. Even with these extraordinary measures it is sometimes difficult to get good paste adhesion to the very corrosion-resistant grids. Grid active material interface problems cause reduced battery life. When lead oxides are used for the paste formulation, the free lead may be corroded preferentially to the grids. For lead antimony and most calcium alloys the grids are corroded preferentially to the free lead giving a good bond between grid and active material even if substantial free lead remains in the cured plate. This paper describes the new corrosion-resistant grid materials, explains the high corrosion resistance, assesses problems of processing corrosion-resistant grids, and suggests modifications of alloy compositions to improve performance.

This paper evaluates the effects of composition on the mechanical properties of conventionally cast, continuously cast, rolled, and con-cast/rolled lead alloys for battery grids. It outlines the effects of deformation on the mechanical properties of alloys for battery grids, and discuses the influence of alloy composition on corrosion.

Lead/acid batteries with tubular grids for the positive electrodes give flatter discharge curves and higher cycle life than batteries using flat plates. Most tubular grids for motive-power batteries contain 9–11 wt.% antimony. Recently, alloys with 1–6 wt.% antimony have been used for reduced maintenance batteries. Sealed, valve-regulated batteries with tubular positive grids for motive power, telecommunications, and UPS service are produced from cast lead-calcium-tin alloys. While these alloys permit the construction of such batteries, cast PbCaSn alloys are significantly inferior to cast PbSb alloys in mechanical properties. Wrought PbCaSn alloys, when used for tubular grids, permit the application of maintenance-free alloys with mechanical properties comparable with, or higher than, those of high-antimony alloys. Wrought materials increase life due to the absence of casting defects. Wrought lead-calcium alloys also offer a dramatic improvement in creep and corrosion resistance compared with conventional cast, tubular, PbCaSn alloys, as well as superior conductivity to cast PbSb. Wrought PbCaSn alloys permit the production of tubular grids at high speed in shapes and forms that are difficult to produce from cast materials. These grid shapes can lead to higher performance, higher discharge-rate, tubular plates. This paper discusses the mechanical properties, grain structure, and corrosion behaviour of cast and wrought PbCaSn and PbSb alloys for tubular grids. It also suggests manufacturing techniques for high performance, wrought, tubular plates.

Recombinant and stationary lead/acid batteries generally use lead—calcium—tin alloys for grids, lead—tin alloys for strap and top lead, and high purity lead for oxide. In many cases, primary lead has been specified for these materials in recombinant batteries because both recycled lead and recycled lead alloys were not thought to be of sufficient purity. With improvements in analytical instruments, it is now possible to determine impurity elements at much lower levels. Because problem elements can be analyzed, refining procedures have now been developed to remove gas-producing impurity elements from recycled lead to levels as low as, or lower than, those in primary lead. These new refinery practices and analytical tests have increased the purity of refined recycled lead, and have permitted the use of recycled lead in recombinant and stand-by batteries. Some elements, deemed to be impurities that must be removed, may in fact be beneficial in alloys for recombinant batteries. This paper examines the purity requirements of lead and lead alloys for recombinant and stand-by batteries, indicates the problem elements, and shows the effects of beneficial elements.

Leadcalcium standby batteries contain free acid, thick grids of low calcium content, and are discharged infrequently. Valve-regulated lead/acid batteries (VRLAs) are deeply discharged, contain immobilized electrolyte, and contain much thinner grids of leadcalciumtin alloys. Tin is added to enhance rechargeability from deep discharge and to enhance the mechanical properties of the alloys, particularly creep resistance. Until 1980, leadcalciumtin alloys suffered from wide variations in grain structure, caused mainly by poor control of the calcium content. The latter is due to calcium oxidation and the inclusion of suspended oxide into the grids. The introduction of aluminium into leadcalcium and leadcalciumtinaluminium alloys prevents calcium loss from the melt. Leadcalciumtinaluminium alloys can be produced to the desired specification without fear of either calcium loss or poor control of grain structure. Aluminium also serves both as a nucleant to significantly reduce the initial cast grain-structure and as a means to enhance the precipitation of calcium in leadcalciumtin alloys. Grain-structure control is now possible even in very high tin-content alloys. Leadcalciumtin alloys with aluminium are not susceptible to penetrating grain boundary corrosion and will become the favored alloys for deep-cycling VRLAs of the future.

Over the past 20 years, a significant number of processes have been developed to recover lead from scrap batteries. These processes recover lead via hydrometallurgical processing of the paste component of the battery followed by electrowinning. A number of pilot plant operations have been conducted, but thus far none of the processes have become operational.

The Advanced Lead-Acid Battery Consortium (ALABC) has produced significant new information regarding the performance and properties of valve-regulated lead-acid batteries. Programs to better understand discharge, recharge, and partial-state-of-charge operation have yielded valuable information on methods to improve battery life. This paper describes how the ALABC work has lead to an improved understanding of how battery capacity degrades with time and how ongoing research may enhance VRLA battery performance and life.

By 2000, most lead-acid, starting/lightening/ignition (SLI) batteries produced in the Western world had made the transition from traditional lead-antimony alloy grids to lead-calcium-based alloys. The automobile requirements for high cranking performance and maintenance-free batteries have accelerated the trend. Cost reductions as well as high numbers of grids-per-battery have led to automated, continuous grid-manufacturing processes which require lead-calcium-based alloys. Higher under-hood temperatures have lead to the introduction of higher tin content and silver additions to lead-calcium alloys to improve battery life. Lead-antimony alloys are still used as grid alloys in SLI batteries around the world. With higher performance requirements in vehicles and newer batteries in the next decade, however, the use of lead-antimony alloys for automobile batteries may decline significantly. This paper describes the operating conditions of automobile batteries in the new millennium and how the grid-production processes and grid alloys have changed to meet the requirements of these batteries.