Investigation of lead base composite anodes produced by accumulative roll bonding

Abstract

Accumulative roll bonding was applied for the first time to fabricate lead-based composites for use as anodes in electrowinning metal production. For this purpose, Pb–Ag, Pb–Co, and Pb–MnO2 systems were investigated. The newly designed anodes were tested for their mechanical properties and microstructure. Maximum bond strength was gained in the presence of 0.125wt% of MnO2 (2.8N/mm) while lower peel strength was achieved when identical percentages of other additives were added. Compared to pure lead sheet, the mechanical properties of lead base composite sheets processed by accumulative roll bonding improved such that tensile strength rose from 10 to 12.6 (MPa) (126% higher), yield strength from 5 (MPa) to 12.4 (MPa) (240% higher), shear yield strength from 10.1 (MPa) to 14.3 (MPa) (42% higher), and hardness from 9.3 (HV) to 78.6 (HV) (8.4times higher). Furthermore, strain decreased from 60% to 8% in the Pb–2% MnO2 8-pass specimen. These improvements in mechanical properties were accompanied by higher stiffness as well as considerable improvements in dimensional stability of the anodes and better creep characteristics. These changes might have been achieved due to the diminished recovery of specimens subjected to sever plastic deformation in the presence of additive particles. The new properties of the lead base composite anode guarantee a lower anodic decay rate, reduced sludge formation, less bath and production contamination, and reduced maintenance and capital costs in lead anode dependent industries.