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Study on Preparation and properties of Pb-Ca-Sn alloy anode materials

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Tutor: GuoZhongCheng
School: Kunming University of Science and Technology
Course: Non-ferrous metallurgy
Keywords: lead alloy anode,tin content,rolling number,rolling direction,surface morphology
CLC: TG339
Type: Master's thesis
Year:  2013
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It was very important to gain the lead calcium tin alloy anode which had the good corrosion resistance, the high electrical conductivity, the good mechanical performance and the long service life in copper electrowinning. Lead calcium tin alloy anode was prepared and studied with different tin content and rolling technology.In this paper, the tin content was respectively controlled at0.6wt%,0.8wt%,1.0wt%,1.2wt%and1.4wt%in lead calcium tin alloy. Lead-calcium-tin alloy was rolled0,1,4and8times by the rolling mill, while the rolling way was one-way rolling or cross rolling.The samples were placed Cu2+45g/L, H2SO4180g/L solution at the current density of200A/m2and held at45¡æfor the electrochemical and corrosion testing.The results by the metallographic analysis and microcosmic hardness testing were shown as followings:the grain size of the alloy surface became large and the hardness of the alloy decreased with increasing the tin content of the Lead calcium tin alloy. It was beneficial to grain the structure refinement and dense of the alloy surface. The hardness of the alloy enhanced when the number of rolling increased.Cross rolling reduced the anisotropy of the alloy surface grain size and increased the hardness of the alloy. Electrochemical test showed that:the PbO and PbSO4of high impedance were not generated on alloy anode surface when tin content increased, and reduced the impedance of anodic films. While, the good electrical conductivity PbOx(1<x<2) were generated that enhanced the conductivity of the alloy anodic film. The alloy anode took place the recrystallization after the deformation with the increase of rolling number. Tin and calcium were advantageous to grain refinement in lead alloy anode which promoted the recrystallization grain size to become thinner and internal organization better, and improved the performance of the alloy anode. Changing the rolling direction, it was more advantageous to generate the recrystallization and regeneration. In addition, the cross rolling strengthened uniformity and isometric organization of alloy anode internal organization, so as to improve the alloy anode internal organization of the performance. The micro structure of different tin content and rolling technology anode was observed by SEM and the phases were analyzed by X-ray diffraction.XRD and SEM test showed that:there were more the electrical conductivity materials to generate on anode film with the increase of the tin content. The porosity of the anodic film gradually increased, which reduced the emergence of the anode passivation phenomenon. It was advantageous to pass in and out of the anodic film for the ions, and improved the conductivity of the anode. The intensity of the alloy anode diffraction peak increased with the increase of rolling number, and the conductive component of PbO and ¦Á-PbO2increased on the anode surface layer. The photo of SEM showed that:the deformation tissue was replaced by the recrystallization grain in the anode internal.The recrystallization grain growed up and formed recrystallization texture, and the organization was relatively uniform. Cross rolling was good at producing uniformity and isometric organization. Corrosion test showed that:the more tin dissolved into the alloy anode corrosion protection layer with the increase of tin content, and reduced the alloy anode of the corrosion efficiency. Changed rolling technology that promoted the alloy anode internal organization and improved the corrosion resistance of the anode materials, meanwhile prolonged the service life of alloy anode material. The tin content was1.2wt%in lead calcium tin alloy.The rolling number was eight times, and the rolling direction was the cross rolling.
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