SURFACE-ANALYSIS OF COMMERCIAL LEAD-ACID-BATTERY GRIDS

Various lead, lead-calcium-tin and lead-antimony battery grids have be en characterized using inductively coupled plasma-atomic emission spec trometry (ICP-AES), X-ray photoelectron spectroscopy (XPS), X-ray diff raction (XRD), and metallographic microscopy. As-received, commerciall y produced grids are encapsulated by a thin film of lead(II) and/or le ad(IV) oxide along with lead(II) hydroxide arising from atmospheric ox idation of lead. Alloy constituents (i.e., Ca, Sn and Sb) segregate to the grid surface during atmospheric oxidation; Sb(III) and/or Sb(V), Sn(II) and Ca(II) have been identified in the grid oxide layer. The in fluence of metallurgical structure on the oxidation-induced segregatio n of minor elements has been evaluated. XPS identified carbonate on th e surfaces of as-received non-antimonial grids, while carbonate was no t detected on antimonial grids. XPS analysis of grids aged in a humidi fied environment - to deliberately invoke the formation of lead carbon ate - confirmed the formation of carbonate on non-antimonial grids, an d the absence of carbonate on antimonial alloys. XRD phase-analysis of aged non-antimonial grids identified the basic lead carbonate hydroce russite (2PbCO(3) . Pb(OH)(2)). A mechanism is proposed for the antimo ny-free effect that is responsible for the premature capacity loss of batteries employing non-antimonial grids.