Grids gravity-cast

Fig. 12.6. (a) Gravity casting of lead antimony grids (left) and lead-caldum expanded metal production (right). 

Fig. 12.7. (a) Gravity-cast grid with diagonal wires and centre lug for improved high-power performance (left) expanded-metal grid (right) (b) Potential distribution of a state-of-the-art... 

Gravity casting of grids is usually employed for the manufacture of flat positive plates. Flat positive lead-calcium-tin grids are more sensitive and more prone to corrosion than tubular grids. Nevertheless, it must be pointed out that even for batteries with flat positive plates, corrosion has been only one of the limiting factors during standby applications. 

Fig. 13.1. Accelerated corrosion test of gravity-cast, lead-calcium-tin grids in sulfuric acid (60°C, 1.26 specific gravity, 1.85 V constant potential against SHE). Change of grid weight measured every 3 weeks without removal of corrosion layer ( ) standard alloy/standard casting (A) improved (in terms of calcium and tin content) alloy/standard casting (o) improved (in terms of calcium and tin content) alloy/improved casting.

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