Grain Boundary Character Distribution Of Pb-based Alloy For Zinc Electrowinning

Pb-based alloys, which are currently used for anode plate in the zinc hydrometallurgy process, exhibit poor resistance to intergranular corrosion and short service life.Pb-Ag alloy and Pb-Ag-Ca-Sr alloy was used as experimental materials in this work. Grain boundary character distribution (GBCD) of alloys was optimized by grain boundary engineering (GBE) technology. The influence of total rolling deformation and heat treatment time on GBCD of Pb-based alloys was investigated. The GBCD optimization results were validated with corrosion test. Meanwhile, the creep resistance and electrochemical performance of Pb-Ag alloy was studied, aimed at the defects of creep deformation and high Ag content. The results show as follows:(1) Rich silver phase distribute striped in the surface of Pb-based alloys specimens. The distribution of Ag element is more homogeneous that is conductive to reduction of oxygen evolution potential and improvement of corrosion resistance with the increase of total deformation.(2) The ∑3n grain boundary of Pb-Ag alloy increase firstly and then decreases with the increase of total deformation. The proportions of ∑3n grain boundary reach highest when the total deformation is 90%. The connectivity of general high angel boundary (HABs) is interrupted sufficiently by special boundary and GBCD is optimized. The ∑3n grain boundary of Pb-Ag-Ca-Sr alloy decreases with the increase of total deformation, the connectivity of HABs cannot be interrupted sufficiently. The E3n grain boundary of Pb-Ag-Ca-Sr alloy increase largely after 270℃ heat treatment for 5-10 min, the connectivity of HABs is interrupted sufficiently by special boundary. However, the GBCD of Pb-Ag alloys cannot be further optimized after 270℃ heat treatment for 5 min. The GBCD of Pb-Ag alloys that contain a large number of ∑3n grain boundary can be obtained through larger rolling deformation. The GBCD of Pb-Ag-Ca-Sr alloys cannot be optimized only by rolling deformation process.To achieve the GBCD optimize, Pb-Ag-Ca-Sr alloys should adopt high temperature heat treatment for short time after rolling.(3) The corrosion rate of Pb-Ag alloys is decreased obviously by GBCD optimizes. The corrosion layer is uniform and compact, the binding force of the corrosion product particles is better, the corrosion pit is smaller. The corrosion resistance of Pb-Ag alloys is improved effectively by GBCD optimizes.(4) The creep resistance of Pb-Ag alloy is better than pure Pb. The dislocation defect of Pb-Ag alloy gradually increased and creep resistance gradually decreased with the increase of total deformation. The dislocation movement is the rate controlling mechanism of Pb-Ag alloy. The creep rate of Pb-Ag alloy greatly decreases after 270℃ heat treatment for 5 min. The creep resistance of Pb-Ag alloy with higher rolling deformation could be improved by high temperature heat treatment for short time.(5) The electrocatalytic activity of oxygen evolution reaction is improved with the addition of Ag element. The oxygen evolution potential gradually reduces with the increase of Ag content. The creep resistance of alloy is improved with the addition of Ag element as well.