Lead—strontium alloys for battery grids

Abstract The metallurgical properties of lead—strontium alloys were studied in relation to the properties required for lead—acid battery grids. The castability of all the alloys tested was as good as the corresponding alloys containing calcium. The mechanical properties of binary alloys containing 0.08% strontium or more and of ternary alloys containing 0.04% strontium or more indicated that these alloys could be handled and processed by normal production techniques. The creep and stress corrosion properties of the binary and ternary alloys were not good enough to consider them for use in deep cycled motive power batteries but the addition of up to 0.25% silver to the ternary alloys gave adequate creep and stress corrosion characteristics for this application. Ternary alloys containing 1–2% tin suffered from severe intergranular corrosion the effects of which could be overcome to some extent either by grain-refining the alloys with cerium mischmetal or by producing a fine-grained alloy grid by wrought techniques. Alloys which could be considered for battery application were lead-0.1% strontium for standby batteries, lead-0.5% tin-0.1% strontium for automotive batteries and lead-0.5% tin-0.01–0.25% silver-0.1% strontium for special motive power batteries if the cost could be afforded. A small addition of aluminium protected all the alloys from loss of alloying constituents in the molten state by oxidation.