Challenges from corrosion-resistant grid alloys in lead acid battery manufacturing

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. (C) 2001 Elsevier Science B.V. All rights reserved.