Homogeneous Microstructure Improving the Mechanical and Electrochemical Properties of Lead Alloys by Stirring Treatment

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In this work, different stirring speed provided during the melt casting of the alloy are tended to obtain lead alloys with different microstructure. The results show that proper stirring speed is beneficial for improving the overall homogeneity of the alloy, however, as the stirring speed is too high, plenty of second phase impurities and defects produced in the lead matrix, which possesses negative effect on the mechanical and electrochemical properties. The most uniform composition and homogeneous microstructure was obtained when the stirring speed is 100 r/min, which is conducive to the decrease of oxygen evolution potential of 30 mV and charge transfer resistance of 22.77%, and the increase of the corrosion resistance of 1.49%, and promote the generation of the uniform and dense PbO 2 protective layer. Lead alloy Mechanical stirring Microstructure Electrochemical property Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Introduction According to the characteristics of zinc resources, zinc extraction can generally be divided into pyrometallurgy and hydrometallurgy techniques, while the characteristics of hydrometallurgy such as high productivity, high efficiency, low environmental pollution and the ability to process low-grade complex ores make it increasingly used in the industry. Currently, over 85% zinc in the world is obtained by electrowinning via hydrometallurgy[ 1 ]. The electrowinning process of zinc consumes nearly 80% of the total energy of the hydrometallurgical process, and the decomposition voltage of zinc sulfate accounts for 70% of the electrolytic voltage in the electrodeposition process of zinc [ 2 ]. therefore, reducing the energy consumption in electrodeposition is the key to reduce the cost. In addition, the high concentration of H 2 SO 4 system is commonly employed in zinc electrowinning industry[ 3 , 4 ]. In this environment, the loose and porous PbO 2 protective film of the traditional lead-silver anode is poor, and the dissolution and shedding of anode mud not only increases the solution resistance, but also contaminates the zinc product of the cathode[ 5 , 6 ]. Strategies are used to overcome the above shortcomings, such as, element doping, microstructure design, different anode matrix application. In terms of alloying, we have mainly developed Ca-system alloy anodes represented by Pb-Ca, Pb-Ag-Ca, and cobalt-system alloys represented by Pb-Co and Pb-Co 3 O 4 have been well developed. Although the addition of Ca enhances the mechanical properties of lead alloys, it does not play a catalytic role for electrochemistry [ 3 ] and even reduces the corrosion resistance of lead anodes [ 4 ]. Although Co exhibits a good electrocatalytic effect and contributes to form a dense layer on the lead alloy surface to enhance the anode life[ 2 , 5 , 6 ], its solubility in the lead melt is extremely low and the complexity of anode preparation limits its large-scale application. The stirring during the melting process improves the fluidity of the molten alloy and enhances the overall homogeneity of the alloy. Investigations have shown that stirring temperature and stirring speed are the most important influencing parameters in the process of mechanical stirring [ 7 , 8 ].Stirring affect crystal nucleation and its quality and change the morphology of the crystal [ 9 , 10 ]. In the melting crystallization process, the crystal growth process is influenced by the migration rate of impurity particles and crystalline particles [ 11 ], and increasing the mass transfer rate by stirring can accelerate the migration of impurity particles and reduce impurity residues. In addition, stirring can accelerate the heat transfer within the melt and prevent structural defects arising from local temperature inhomogeneity. In this paper, Pb-Ag-Ca alloys were prepared by the melting method, and the stirring speed was incorporated using a mechanical stirring device in the molten state to investigate the microstructure of the alloys caused by different stirring speed and its effect on the mechanical and electrochemical properties of the obtained alloy. The results reveal that 100r/min speed leads to the most homogeneous microstructure, which is beneficial for decreasing the oxygen evolution potential and charge transfer resistance, and increasing the corrosion resistance of lead alloy. Furthermore, the uniform composition and homogeneous structure promotes the generation of PbO 2 surface protective layer. Experimental section 2.1 Sample preparation Firstly, 2/3 of the required pure lead was added into the intermediate frequency furnace, where the temperature was rapidly increased the temperature to 500°C. After all the pure lead is melted, lead-silver, lead-calcium intermediate was introduced into the system. When all the alloys are melted, under the same conditions, the mechanical stirring device was adjusted to stir for 1min at different stirring speeds. Subsequently, NH 4 Cl is added for slag removal, and the slag is fully fished out before casting. The Ag and Ca contents of the resulting alloy are measured to ensure that the final alloy keep the same content of each element, and the process is schematically shown in Fig. 1 . Firstly, we cast the alloy with the same content of Pb-Ag-Ca at the mechanical stirring speed of 0r/min, 100r/min, 200r/min and 400r/min respectively (Fig. 2 ). According to the uniformity of the alloy cross-section, the overall uniformity of the alloy rises and then decreases with the increase of the stirring speed. The most uniform alloy can be obtained when the mechanical stirring speed is around 100r/min. The reason for this is the inhomogeneous composition of the melt obtained without stirring during melting. When the stirring speed is too high, the lead melt will be in full contact with the air to produce oxidation and a large amount of slag on the surface of the melt; at the same time, a large amount of oxide is generated inside the melt to make the cast alloy delamination. Therefore, we reduced the stirring speed interval and remelted the lead alloy for subsequent experiments. The obtained alloys were numbered as samples 1, 2, 3, 4 and 5. The corresponding elemental contents and different stirring speeds are listed in Table 1 . Table 1 Elemental alloy content in different samples Sample Ag(%) Ca(%) Stirring speed(r//min) 1 0.30 0.07 0 2 0.30 0.07 50 3 0.30 0.07 100 4 0.30 0.07 150 5 0.30 0.07 200 2.2 Metallographic oreparation Small pieces of 10mm×10mm×10mm alloy are cut from the alloy blocks via wire cutting after rolling, which was then encapsulated with resin, exposing only the surface to be observed. The surface was sandpapered until no obvious rough scratches. The sample was then placed on the clean flannel of the polishing machine for polishing until the alloy surface displayed a bright mirror finish, and the polishing solution was used with 0.5 µm diamond spray polish. The use of corrosion solution (Acetic acid: hydrogen peroxide = 4:1) will be bright surface corrosion out of the metallographic organization, and quickly wash away the residual corrosion solution with alcohol, dry with a hair dryer. 2.3 Mechanical properties test After observing the metallographic phase of the sample, the sample was put it on the flannel of the polishing machine to polish the surface corrosion layer. Then, the hardness was measured on the microhardness tester (HV-1000V). The tensile strength and plastic elongation strength of the material are tested by tensile test (UTM4304SLXY). After the specimen fails under tensile load, the percentage of the total elongation to the original length of the specimen is the elongation of the section. Since the lead alloy has no obvious yield point, the yield limit is taken as the stress value that produces 0.2% residual deformation. 2.4 Electrochemical tests The comparative experiment mainly uses cyclic voltammetry, Tafel curves, anodic polarization curves, and AC impedance spectroscopy techniques to study the surface states of lead alloys in 150 g/L H 2 SO 4 , 50 g/L Zn 2+ solutions. The alloy properties were characterized by using the peak current peak potential of redox peaks, oxygen evolution overpotential, charge transfer resistance, and surface roughness. The electrochemical test adopts a standard three-electrode system, the test temperature is 35℃, the sample working area is 1.0cm 2 , the reference electrode is saturated mercurous sulfate (MSE): Hg, Hg 2 SO 4 /sat.K 2 SO 4 , and the auxiliary electrode is 1cm 2 platinum piece. The working electrode was connected to the auxiliary electrode by a saturated potassium sulfate agar salt bridge. The potential values measured electrochemically in the tests are both with respect to MSE. 2.5 Accelerated corrosion test Accelerated corrosion tests were conducted in solution containing 150g/L H 2 SO 4 , 0.8g/L Cl − : under current density 4000A/m 2 with corrosion time 120 h, where the anode size was 50 mm × 30 mm × 7.27 mm. The corrosion system adopts a liquid circulation system, the anode is a multi-polymer lead alloy plate prepared at different stirring speeds, and the cathode is a copper-plated titanium plate. Two pieces of each alloy were taken for accelerated corrosion experiments. After the corrosion test, one piece was taken to observe the surface morphology of the corrosion layer with SEM (TESCAN VEGA4) and XRD (Bruker D2); the other piece was boiled with a 1:1 mixed solution of NaOH and glucose to remove the oxide layer on the surface, and dried and weighed to observe the corrosion weight loss. The oxide layer on the surface of the other anode was washed off using a 1:1 boiling solution of NaOH and glucose, dried and weighed to observe the corrosion weight loss. Results and Discussion 3.1 Metallographic pictures The metallographic images of the rolled Pb-Ag-Ca alloys prepared under different stirring speeds are shown in Fig. 3 . The grain boundaries of the rolled alloys are significantly elongated. There are dotted or long bright particles at the grain boundaries of different alloys, and these particles may be the intermetallic compound Pb 3 Ca [ 12 ]. It can be seen from Fig. 3 , aggregation of intermetallic compounds is observed in the alloy matrix without stirring or with higher stirring speed (200r/min) (circled in Fig. 3 a and e). When the stirring speed is moderate (50 r/min ~ 150 r/min), the intermetallic compounds are evenly distributed in the matrix without obvious aggregation. This phenomenon is ascribed to the fact that the intermetallic compounds in the unstirred are deposited at the bottom of the melt or float on the surface of the metal melt, leading to aggregation, while when the stirring speed is too high, the higher quality intermetallic compounds produced again due to the centrifugal action, which decreases the alloy uniform. The aggregation of intermetallic compounds causes the differences of the composition in various parts of the alloy, resulting in the decrease in its corrosion resistance and local corrosion during the working procedure. Alloys with uniform composition possesses higher corrosion resistance, resulting in uniform corrosion during the working procedure. 3.2 Hardness test The hardness values of each alloy at five different positions and average hardness values for each alloy are shown in Fig. 4 . Among them, the bar chart represents the hardness values of five test points of different samples, and the line chart shows the change trend of average hardness. In Fig. 4 , the average hardness value of the alloy decreases with the increase of stirring speed, but the hardness values across the alloy become closer compared with sample 1. The similar value of the hardness after stirring originates from the uniformly distributed alloy elements. When stirring too fast or without stirring, the hardness of the produced intermetallic compound and its surrounding area is higher than other domain, and the area without intermetallic compound is close to that of pure lead, leading to the difference of hardness in samples. Therefore, the moderate stirring speed causes the more uniform distribution of intermetallic compounds in the matrix, leading to the more uniform and higher hardness. 3.3 Tensile measurement Add tensile stress to both ends of the sample prepared at different stirring speeds and record the relationship between stress and strain. Figure 5 (a) shows the stress-strain curve of the alloy during stretching, and Fig. 5 (b) shows the variation of alloy strength values. From Fig. 5 , it can be seen that with the increase of stirring speed, The tensile strength and yield strength of the alloys show a trend of first increasing and then decreasing with the increase of the stirring speed. When the stirring speed reaches 100r/min, the alloy obtained the maximum tensile strength and the maximum yield strength of 40.73Mpa and 28.50Mpa, respectively. The optimal properties stem from the overall uniformity of the alloy. When subjected to tensile load, the entire cross-section of the alloy is uniformly stressed, resulting in an increase in strength. The unsuitable stirring speed leads to the poor internal uniformity of the alloy. When subjected to external loading, local stress is easily generated, and the tensile strength and yield strength of the alloy decrease. 3.4 CV investigation Figure 6 records the cyclic voltammograms of the Pb-Ag-Ca alloy samples with different microstructure. As observed, the profiles contain two main oxidation peaks and two reduction peaks regardless of whether stirring was performed during the preparation process, indicating that the microstructure shows little affect on the main reactions occurring on the substrate. The reaction represented by the oxidation peak a is: Pb + SO 4 2− -2e − =PbSO 4 [ 13 ]. Potential range [-0.8V, 1.0V] corresponds to PbSO 4 passivation range. Oxidation peak b represents the evolution of oxygen, the conversion of PbSO 4 to β-PbO 2 and the conversion of PbO to α-PbO 2 . The reduction peak c is the reduction of PbO 2 to PbSO 4 . The higher the peak, the higher the content of PbO 2 in the surface film [ 14 ]. The reduction peaks d and dʹ are the reduction reactions of PbO and PbSO 4 to metallic lead. It can be concluded from Fig. 6 that with the increase of stirring speed, the intensity of oxidation peak b first increases and then decreases, and reaches the maximum value at 100 r/min, indicating that the anode activity is the highest at this time, and the surface generation of PbO 2 and oxygen evolution reaction are violent. This phenomenon is ascribed to the increasing surface roughness of the anode and the uniformity of the distribution of the intermetallic compounds in the alloy. 3.5 LSV investigation The anodic polarization curve is one of the important methods to investigate the electrowinning process. The measured anodic polarization curve is subjected to Tafel analysis to obtain important reaction kinetic parameters such as oxygen evolution overpotential and apparent exchange current density. The potential values used for Tafel analysis are calculated by the equation below [ 15 ]: η = E + 0.640 − 1.242 (1) where E (MSE) is oxygen evolution potential in the anodic polarization curve, 0.640 V(SHE) means the standard potential of MSE, 1.242 V stands for oxygen evolution reaction potential at 35°C in a mixed solution of 50 g/L Zn 2+ and 150 g/L H 2 SO 4 . After processing the anodic polarization curve, it can be converted into the form of Tafel equation ( η = a + blg J ), where η, a, b, J represent the oxygen evolution reaction overpotential, Tafel constant, Tafel slope, and electrode surface current density, respectively. By fitting a linear curve to the relationship between η and lg J , the values of a and b can be obtained[ 16 – 18 ]. When the value of η is 0, the exchange current density J 0 can be obtained from the above equation. It can be known from the relevant electrochemical theory [ 19 ]. J 0 represents the degree of difficulty in the occurrence of reactions on the electrode surface, where a high exchange current density indicates that the polarization of the electrode is less likely, the reversibility of the electrode is improved, and the reactions on the electrode are more likely to occur. Figure 7 (a) shows the anodic polarization curves of the alloy samples with different microstructure. With the increase of stirring speed, the oxygen evolution potential of anode decreases first and then increases. When the stirring speed reaches 150 r/min, the oxygen evolution potential at the current density of 50mA/cm 2 reaches the lowest value of 1.559V, and when the stirring speed reaches 200 r/min, the oxygen evolution potential reaches the highest value of 1.606V. Although the oxygen evolution potential of 100 r/min alloy is not the lowest (1.569V), it is also close to 1.559V. The logarithm of the current density log i for different alloys was then plotted against the overpotential η, and the relevant kinetic parameters were listed in the Table 2 . Table 2 Oxygen evolution kinetic parameters of alloy samples rolled at different stirring speeds Sample 0r/min 50r/min 100r/min 150r/min 200r/min a 1.216 1.215 1.200 1.248 1.193 b 0.166 0.160 0.166 0.211 0.142 J 0 (A/cm 2 ) 5.101×10 − 8 2.661×10 − 8 6.436×10 − 8 1.260×10 − 6 4.190×10 − 9 The data in Table 2 indicate that with the increase of stirring speed, both a and b fluctuate in a small range, but both reach the lowest value when the rotation speed is 200r/min. The values of a and b represent the level of battery voltage and anode overpotential, respectively [ 18 ]. The smaller the values of a and b, the lower the total energy consumption, so the energy consumption is the lowest when the rotation speed is 200 r/min. However, the J 0 also reached the minimum value at this time, indicating that the reversibility of the electrode reaction was poor at this time, and the reaction on the electrode was more difficult. 3.6 Tafel curves Figure 8 shows the Tafel curves of alloys prepared at different stirring speeds. It can be seen from Fig. 8 that after adding the stirring process, the alloy curves all move forward towards the X-axis. The self-corrosion potential E corr and self-corrosion current density I corr values of the anode sample obtained from Fig. 8 are shown in Table 3 . Table 3 Self-corrosion potential and current density of electrodes at different speeds Sample 0r/min 50r/min 100r/min 150r/min 200r/min E corr(V.MSE) -0.989 -0.968 -0.968 -0.968 -0.970 J corr(A/cm2) 3.64*10 − 4 1.97*10 − 4 1.63*10 − 4 2.18*10 − 4 2.56*10 − 4 According to Faraday's law, the relationship between self-corrosion current density and metal self-corrosion rate is expressed as follows [ 18 ]: V = M J corr / nF (2) where V is corrosion rate, M represents molar mass of metal, J corr stands corrosion current density, n means metal valence, F stands for Faraday constant. Theoretically, large anode corrosion potential means better corrosion resistance of the anode and less possibility of corrosion. High corrosion current density means that the higher the corrosion rate, the worse the corrosion resistance of the anode. As shown in Table 3 , the corrosion current density of 0r/min alloy is the highest (3.64×10 − 4 A/cm 2 ), and the current density of 100r/min alloy is the lowest (1.63×10 − 4 A/cm 2 ). The corrosion potential is the lowest value in the range of 50 r/min to 150 r/min (-0.968V). 3.7 AC Impedance Spectrum The AC impedance spectra of Pb-Ag-Ca alloys at different stirring speeds measured in 50g/L Zn 2+ , 150g/L H 2 SO 4 electrolyte and equivalent circuit diagram of five kinds of anode fitting AC impedance are shown in the Fig. 9 . It can be seen from the curves that the AC impedance spectra of the four anode oxygen evolution reactions are similar, all of which are semicircles, so the charge transfer is still the control step. The relationship between the double-layer capacitance C dl without solution compensation and the charge transfer resistance usually satisfies the following relationship[ 19 , 20 ]: Q dl =( C dl ) n [( R s ) −1 +( R t ) −1 ] (1− n ) (3) R s stands for the resistance of the solution between the working electrode and the reference electrode, R t represents charge transfer resistance in the electrochemical reaction process charge transfer resistance, CPE refers to an element of constant phase element for the behavior of the electrode and electrolyte interface, which is often used to fit experimental data instead of capacitance. In addition, C dl can be used as a relative method to characterize electrode surface roughness, and its relationship with anode roughness ( R F) can be calculated by the following formula[ 21 , 22 ]: R F = C dl / C ⁎ (4) Where C ⁎ represents the capacitance reference value. For a smooth mercury electrode, C ⁎ is 20 µF·cm − 2 . The roughness values obtained from anodized films are often used to characterize the microscopic topography of electrodes [ 23 ]. Equivalent circuit fitting is performed on the impedance spectrum, and the fitting data are shown in the Table 4 . Table 4 Equivalent circuit parameters of AC impedance spectrum of different anode materials Anode specimens R s /(Ω·cm 2 ) R t /(Ω·cm 2 ) Q dl /(Ω −1 ·cm − 2 ·s n ) n C dl /(µF·cm − 2 ) R F 0r/min 0.931 17.17 0.0195 0.873 10799 539 50r/min 0.873 14.03 0.0278 0.840 13534 676 100r/min 0.945 13.26 0.0286 0.859 15633 781 150r/min 0.876 9.198 0.0235 0.859 12239 611 200r/min 0.88 10.55 0.0234 0.884 13911 695 The EIS diagram shows that with the increase of the stirring speed, the diameter of the semicircle shows a decreasing trend, and reaches the lowest value when the rotational speed is 150 r/min. The charge transfer resistance R t also shows the same trend. When the rotational speed is 150 r/min, the R t value reaches the minimum, about half of the 0 r/min alloy. The smaller the R t , the smaller the charge transfer resistance, and the easier the electrochemical reaction occurs [ 24 ]. In addition, as the stirring speed increases, the surface roughness of the anode first increases and then decreases, and the R F reaches the maximum value at 100 r/min. It is generally believed that the roughness is related to the oxygen evolution area of the oxide layer on the anode surface, and the larger the roughness, the more oxygen release area on the anode surface, and the easier the oxygen evolution reaction. 2.8 Accelerated corrosion investigation Table 5 reveals the accelerated corrosion weight loss rate of alloys after rolling. Apparently, with the increase of stirring speed, the anodic corrosion rate first decreases and then increases, reaching the lowest value at the stirring speed of 100 r/min, which is consistent with the Tafel test results. The corrosion mechanism is shown in Fig. 10 . In the melting process, with low stirring speed or without stirring, the intermetallic compounds and impurities are going to be deposited at the bottom of the melt, leading to the difference of the properties in the upper and lower surfaces of the alloy after the melt solidifies. The corrosion starts from the place where there are many impurities and compounds and penetrates into the interior. The moderate stirring speed results in the uniform microstructure of the alloys, therefore, uniform corrosion occurs on the surface of the alloy, and the corrosion rate slows down. As the there is a higher stirring speed, various impurities and substances produced at the edge and the center of the alloy, giving rise to different properties inside and outside the alloy. At the beginning, the corrosive solution penetrates into the interior of the substrate from the edge of each substance, and the oxide layer fall off seriously. After the external oxide layer is corroded, the internal pure lead is exposed to the working environment, and the corrosion resistance is greatly reduced. Then, the surface of another anode after corrosion was rinsed with first-grade water, and its surface corrosion layer was further observed by XRD and SEM. Table 5 Accelerated corrosion weight loss rate after rolling of alloys with different stirring speeds Sample Weight loss rate(%) 0r/min 7.8557 50r/min 6.6988 100r/min 6.3632 150r/min 6.4069 200r/min 6.8129 2.9 Surface morphology of alloy corrosion coatings The surface morphology of the alloy prepared at different stirring speeds after accelerated corrosion is presented in Fig. 11 . With the increase of stirring speed, the uniformity and denseness of the anode surface film layer first increased and then decreased. The film denseness was best at the stirring speed of 100r/min, and then the film denseness and flatness gradually decreased. When the flatness of the film layer decreases and the surface pores increase, the electrolyte will pass through the surface pores of the film layer and contact with the substrate, and the film layer covering the surface of the substrate cannot play a protective role, which greatly reduces the corrosion resistance of the alloy. The result is consistent with the previous test. 2.10 XRD after anodic corrosion Figure 12 shows the X-ray diffraction pattern of the surface corrosion layer after anodic corrosion. In Fig. 12 , the anodic oxide films of each alloy are mainly composed of PbSO 4 (82-1854)、PbO(76-1796)、α-PbO 2 (45-1416)、β-PbO 2 (41-1492), but the material content of each anode layer is different. The preferred growth directions of α-PbO 2 are (111) plane and (110) plane, respectively, and the preferred growth orientation of β-PbO 2 is the (110) plane. With the increase of stirring speed, the peak intensity of α-PbO 2 is always high and fluctuates in a small range, while the peak intensity of PbSO 4 first increases and then decreases the highest intensity of PbSO 4 is obtained until the stirring speed reach 100 r/min. The content of β-PbO 2 has no obvious change, but its peak intensity is higher for the alloy stirred at 100r/min. The reason is that the main reaction that occurs a few days before the formation of the anodic film is the conversion of PbSO 4 to α-PbO 2 . At this time, the higher peak intensity of α-PbO 2 is also reflects the better performance of the anode surface film. The high peak intensity of β-PbO 2 at the 100 r/min alloy anode is due to the large amount of PbSO 4 covering the alloy surface under this condition, which leads to an increase in the surface current density and potential in the region not covered by PbSO 4 , and due to the high oxygen evolution overpotential on the lead surface, the following two PbO 2 generation reactions occur first [ 25 ], leading to an increase in β-PbO 2 content. PbSO 4 + H 2 O-2e = = PbO 2 + H 2 SO 4 + 2H + ԑ 0 =1.926v (5) Pb + 2H 2 O-4e = = PbO 2 + 4H + ԑ 0 =0.896v (6) Conclusion Lead alloys with different microstructure was successfully prepared by melting method. During the whole preparation procedure, with or without stirring affects the microstructure of the alloy, to further affects the mechanical properties, electrochemical properties, and corrosion resistance properties of lead alloy anodes. Suitable stirring speed leading to a uniform composition and homogeneous microstructure, as the speed reaches 100r/min, the lead alloy possesses the highest tensile strength and yield strength compared with other samples, which originates from the homogeneous microstructure of the alloy. When stirring speed is too high, more second phases produced in the matrix, causes the bad properties. The decreased oxygen evolution potential of 30 mV and charge transfer resistance of 22.77%, and increased corrosion resistance of 1.49% also beneficial from the uniform composition and homogeneous microstructure of the alloy as the speed is 100r/min. Furthermore, the uniform composition surface of the lead alloy is conducive to generate a uniform and dense PbO 2 protective layer, reducing the damage of the electrolytic solution to the interior of the substrate and improving the corrosion resistance of the anode. Therefore, preparation process depends on the microstructure of the matrix, homogeneous microstructure plays a key role in improving the mechanical and electrochemical of the lead alloy matrix. Declarations Credit authorship contribution statement Cheng Jiang: investigation, conceptualization, data curation, formal analysis and writing original draft. Yingping Zhou and Ruidong Xu: investigation, conceptualization and data curation. Buming Chen , Jun Guo and Yi Tao: investigation, conceptualization, validation, writing-review & editing and supervision. Hui Huang , Chao Gao and Zhongcheng Guo: resources, funding acquisition, validation and supervision. Declaration of Interest There is no conflict of interest to declare. Acknowledgement This research is funded by the National Natural Science Foundation of China (No. 51564029, 22262017 and 51874154), The Technology Innovation Talents Project of Yunnan Province (No.2019HB111). References H.T. Yang, H.R. Liu, Z.C. 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Takahashi, M. Nagai et al (2013), Characteristics of Pb-based alloy prepared by powder rolling method as an insoluble anode for zinc electrowinning, Hydrometallurgy 136: 78-84. http://dx.doi.org/https://doi.org/10.1016/j.hydromet.2013.03.011 X.Y. Zhou, S. Wang, J. Yang et al (2017), Effect of cooling ways on properties of Al/Pb-0.2%Ag rolled alloy for zinc electrowinning, TRANSACTIONS OF NONFERROUS METALS SOCIETY OF CHINA 27: 2096-2103. http://dx.doi.org/10.1016/S1003-6326(17)60235-8 H.T. Yang, Z.C. Guo, B.M. Chen et al (2014), Electrochemical behavior of rolled Pb-0.8%Ag anodes in an acidic zinc sulfate electrolyte solution containing Cl - ions, HYDROMETALLURGY 147: 148-156. http://dx.doi.org/10.1016/j.hydromet.2014.05.004 Y. Lai, Y. Li, L. Jiang et al (2012), Electrochemical behaviors of co-deposited Pb/Pb–MnO 2 composite anode in sulfuric acid solution – Tafel and EIS investigations, Journal of Electroanalytical Chemistry 671: 16-23. http://dx.doi.org/https://doi.org/10.1016/j.jelechem.2012.02.011 B. Chen, Z. Guo, H. Huang et al (2009), Effect of the current density on electrodepositing alpha-lead dioxide coating on aluminum substrate, Acta Metallurgica Sinica (English Letters) 22: 373-382. http://dx.doi.org/https://doi.org/10.1016/S1006-7191(08)60111-8 X.C. Zhong, X.Y. Yu, L.X. Jiang et al (2015), Influence of Fluoride Ion on the Performance of Pb-Ag Anode During Long-Term Galvanostatic Electrolysis, JOM 67: 2022-2027. http://dx.doi.org/10.1007/s11837-015-1550-1 U. Casellato, S. Cattarin, M. Musiani (2003), Preparation of porous PbO 2 electrodes by electrochemical deposition of composites, ELECTROCHIMICA ACTA 48: 3991-3998. http://dx.doi.org/10.1016/S0013-4686(03)00527-9 Y.A. Liu, H.L. Liu, J. Ma et al (2011), Investigation on electrochemical properties of cerium doped lead dioxide anode and application for elimination of nitrophenol, ELECTROCHIMICA ACTA 56: 1352-1360. http://dx.doi.org/10.1016/j.electacta.2010.10.091 Z. Shuiping, L. Yanqing, J. Liangxing et al (2008), Anodization behavior on Pb-Ag-Ca-Sr alloy during zinc electrowinning, The Chinese Journal of Nonferrous Metals 18: 1342-1346. https://doi.org/10.3321/j.issn:1004-0609.2008.07.028 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4519418","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":315541919,"identity":"9f6d4e9d-9573-419f-ae7b-8a3231673422","order_by":0,"name":"Cheng Jiang","email":"","orcid":"","institution":"Kunming University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Cheng","middleName":"","lastName":"Jiang","suffix":""},{"id":315541920,"identity":"d5f84571-816c-4d32-bc9e-9dd47d2a391b","order_by":1,"name":"Yingping Zhou","email":"","orcid":"","institution":"Kunming University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Yingping","middleName":"","lastName":"Zhou","suffix":""},{"id":315541921,"identity":"968a629a-10f7-4316-9f35-1d40412ad532","order_by":2,"name":"Ruidong Xu","email":"","orcid":"","institution":"Kunming University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Ruidong","middleName":"","lastName":"Xu","suffix":""},{"id":315541922,"identity":"8aa5055d-ae7a-46bf-bd72-7c5f00790440","order_by":3,"name":"Buming Chen","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAzUlEQVRIiWNgGAWjYBACAyBmBmI5CQifmXgtxkAtjA0kaUmcQbQWc4nsxM8FFXfSZ85If/6AocI6sYH97AG8Wixn5G6WnnHmWe5siRzDBoYz6YkNPHkJ+B12I3cbM2/b4dx5EjmMDYxthxMbJHgMiNDy73C6nET6wwbGf0RraTicIC2RYNjA2ECEFsuet5uleY4dNpzZ88ZwRsKxdOM2nhz8WszZczd+5qk5LC9xPP3Bhw811rL97Gfwa0EFCUDMRoL6UTAKRsEoGAU4AADFQ0T/knvhagAAAABJRU5ErkJggg==","orcid":"","institution":"Kunming University of Science and Technology","correspondingAuthor":true,"prefix":"","firstName":"Buming","middleName":"","lastName":"Chen","suffix":""},{"id":315541923,"identity":"73e65e48-6320-4153-bfb4-8bb3277d3dee","order_by":4,"name":"Hui Huang","email":"","orcid":"","institution":"Kunming University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Hui","middleName":"","lastName":"Huang","suffix":""},{"id":315541924,"identity":"b4ab6ed1-ff23-43a6-9e6b-7d30a6a332dc","order_by":5,"name":"Jun Guo","email":"","orcid":"","institution":"Kunming University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Jun","middleName":"","lastName":"Guo","suffix":""},{"id":315541925,"identity":"833f79f7-76eb-418f-8836-19e1b44599b6","order_by":6,"name":"Yi Tao","email":"","orcid":"","institution":"Kunming University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Yi","middleName":"","lastName":"Tao","suffix":""},{"id":315541926,"identity":"bf01eaf9-85e0-439e-9b20-3dddb9a8149b","order_by":7,"name":"Chao Gao","email":"","orcid":"","institution":"Kunming University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Chao","middleName":"","lastName":"Gao","suffix":""},{"id":315541927,"identity":"026b4a02-4de0-4fa5-ae38-805e786b6f72","order_by":8,"name":"Zhongcheng Guo","email":"","orcid":"","institution":"Kunming University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Zhongcheng","middleName":"","lastName":"Guo","suffix":""}],"badges":[],"createdAt":"2024-06-03 05:35:58","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4519418/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4519418/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":58551033,"identity":"daa3052f-1282-4bf6-8bd2-369416322ed1","added_by":"auto","created_at":"2024-06-18 06:50:25","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":173835,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic diagram of the preparation of Pb-Ag-Ca alloy at different speeds\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-4519418/v1/341fbeed2ff72300857beef0.png"},{"id":58551034,"identity":"fe177199-01aa-4c4f-b33b-ddf27a633f9b","added_by":"auto","created_at":"2024-06-18 06:50:25","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1175995,"visible":true,"origin":"","legend":"\u003cp\u003eLead alloy cross sections obtained at different stirring speeds. (a) 0r/min; (b) 100r/min; (c) 200r/min; (d) 400r/min;\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-4519418/v1/b974db04de6754c1f96eb5c5.png"},{"id":58551022,"identity":"9dc77463-96b4-4a6d-8dc1-9c36a8eeda60","added_by":"auto","created_at":"2024-06-18 06:50:25","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":3475610,"visible":true,"origin":"","legend":"\u003cp\u003eMetallographic images of alloys with different stirring speeds. (a)0r/min; (b)50r/min; (c)100r/min; (d)150r/min; (e)200r/min\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-4519418/v1/4c671ace424bb7f0826b7740.png"},{"id":58551831,"identity":"4c725d1d-9ed1-4e8e-8e44-3bb83502ce02","added_by":"auto","created_at":"2024-06-18 06:58:25","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":66323,"visible":true,"origin":"","legend":"\u003cp\u003eThe hardness chart of five test points for each alloy and the trend chart of average hardness\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-4519418/v1/943ac505e42d94d53f063d8c.png"},{"id":58551832,"identity":"b416dd46-8dfc-4d82-9421-ec0ccefdba49","added_by":"auto","created_at":"2024-06-18 06:58:25","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":103791,"visible":true,"origin":"","legend":"\u003cp\u003eTensile diagram of lead alloy anode samples prepared at different stirring speeds\u003c/p\u003e\n\u003cp\u003e(a) Stress-strain relationship diagram; (b)Alloy strength test chart.\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-4519418/v1/9f908b8fd642326b4c96e007.png"},{"id":58551830,"identity":"8bd1011b-6d51-4a17-8fbb-1a3079f4b017","added_by":"auto","created_at":"2024-06-18 06:58:25","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":142503,"visible":true,"origin":"","legend":"\u003cp\u003eCyclic voltammograms of alloy anode samples prepared at different stirring speeds\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-4519418/v1/628582c354513d1e0f99d097.png"},{"id":58551025,"identity":"d7d958e2-21f7-4e72-b2bd-f890977f4ac2","added_by":"auto","created_at":"2024-06-18 06:50:25","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":321497,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Anodic polarization curves of alloy samples prepared at different stirring speeds; (b) Fitting curve of overpotential and logarithm of current density in OER strongly polarized region\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-4519418/v1/eb45bf95f18c23b257c510ca.png"},{"id":58551023,"identity":"332e0f34-bb26-4b97-b872-5eab3bdaba3f","added_by":"auto","created_at":"2024-06-18 06:50:25","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":105537,"visible":true,"origin":"","legend":"\u003cp\u003eTafel curves of Pb alloys at different stirring speeds\u003c/p\u003e","description":"","filename":"floatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-4519418/v1/6c0046ed44662b18b53e9570.png"},{"id":58551029,"identity":"ab17d80f-82a5-4a4e-95da-d91bf7dc2248","added_by":"auto","created_at":"2024-06-18 06:50:25","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":232233,"visible":true,"origin":"","legend":"\u003cp\u003eEIS of alloys obtained at different stirring speeds\u003c/p\u003e","description":"","filename":"floatimage9.png","url":"https://assets-eu.researchsquare.com/files/rs-4519418/v1/1a781616b0bf84543e98e80d.png"},{"id":58551032,"identity":"5df10c97-309a-4567-95b3-dccf363ca4b6","added_by":"auto","created_at":"2024-06-18 06:50:25","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":154262,"visible":true,"origin":"","legend":"\u003cp\u003eCorrosion mechanism after rolling of alloy with different stirring speed\u003c/p\u003e","description":"","filename":"floatimage10.png","url":"https://assets-eu.researchsquare.com/files/rs-4519418/v1/c4d7077b70888d07552864ae.png"},{"id":58552183,"identity":"904e7b29-21a3-4623-a69c-e589b6648012","added_by":"auto","created_at":"2024-06-18 07:06:25","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":1048686,"visible":true,"origin":"","legend":"\u003cp\u003eSEM after accelerated corrosion of the alloy obtained at different stirring speeds. (a)0r/min(*1000); (b)50r/min(*1000); (c)100r/min(*1000); (d)150r/min(*1000); (e)200r/min(*1000)\u003c/p\u003e","description":"","filename":"floatimage11.png","url":"https://assets-eu.researchsquare.com/files/rs-4519418/v1/23bd2cb77255b4520171e062.png"},{"id":58551028,"identity":"2b7b97d7-c0c3-44ae-a486-2dc6a8356d9f","added_by":"auto","created_at":"2024-06-18 06:50:25","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":95851,"visible":true,"origin":"","legend":"\u003cp\u003eXRD after accelerated corrosion at different stirring speeds\u003c/p\u003e","description":"","filename":"floatimage12.png","url":"https://assets-eu.researchsquare.com/files/rs-4519418/v1/54673686632db89fddc47447.png"},{"id":64850217,"identity":"05603432-3373-4bbd-9191-7acc2cfa8415","added_by":"auto","created_at":"2024-09-19 13:53:43","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":9932410,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4519418/v1/a366f9b5-58bb-48ae-82bd-8357cbf6bae9.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Homogeneous Microstructure Improving the Mechanical and Electrochemical Properties of Lead Alloys by Stirring Treatment","fulltext":[{"header":"Introduction","content":"\u003cp\u003eAccording to the characteristics of zinc resources, zinc extraction can generally be divided into pyrometallurgy and hydrometallurgy techniques, while the characteristics of hydrometallurgy such as high productivity, high efficiency, low environmental pollution and the ability to process low-grade complex ores make it increasingly used in the industry. Currently, over 85% zinc in the world is obtained by electrowinning via hydrometallurgy[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. The electrowinning process of zinc consumes nearly 80% of the total energy of the hydrometallurgical process, and the decomposition voltage of zinc sulfate accounts for 70% of the electrolytic voltage in the electrodeposition process of zinc [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. therefore, reducing the energy consumption in electrodeposition is the key to reduce the cost. In addition, the high concentration of H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e system is commonly employed in zinc electrowinning industry[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. In this environment, the loose and porous PbO\u003csub\u003e2\u003c/sub\u003e protective film of the traditional lead-silver anode is poor, and the dissolution and shedding of anode mud not only increases the solution resistance, but also contaminates the zinc product of the cathode[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Strategies are used to overcome the above shortcomings, such as, element doping, microstructure design, different anode matrix application. In terms of alloying, we have mainly developed Ca-system alloy anodes represented by Pb-Ca, Pb-Ag-Ca, and cobalt-system alloys represented by Pb-Co and Pb-Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e have been well developed. Although the addition of Ca enhances the mechanical properties of lead alloys, it does not play a catalytic role for electrochemistry [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e] and even reduces the corrosion resistance of lead anodes [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Although Co exhibits a good electrocatalytic effect and contributes to form a dense layer on the lead alloy surface to enhance the anode life[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e], its solubility in the lead melt is extremely low and the complexity of anode preparation limits its large-scale application.\u003c/p\u003e \u003cp\u003eThe stirring during the melting process improves the fluidity of the molten alloy and enhances the overall homogeneity of the alloy. Investigations have shown that stirring temperature and stirring speed are the most important influencing parameters in the process of mechanical stirring [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e].Stirring affect crystal nucleation and its quality and change the morphology of the crystal [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. In the melting crystallization process, the crystal growth process is influenced by the migration rate of impurity particles and crystalline particles [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e], and increasing the mass transfer rate by stirring can accelerate the migration of impurity particles and reduce impurity residues. In addition, stirring can accelerate the heat transfer within the melt and prevent structural defects arising from local temperature inhomogeneity.\u003c/p\u003e \u003cp\u003eIn this paper, Pb-Ag-Ca alloys were prepared by the melting method, and the stirring speed was incorporated using a mechanical stirring device in the molten state to investigate the microstructure of the alloys caused by different stirring speed and its effect on the mechanical and electrochemical properties of the obtained alloy. The results reveal that 100r/min speed leads to the most homogeneous microstructure, which is beneficial for decreasing the oxygen evolution potential and charge transfer resistance, and increasing the corrosion resistance of lead alloy. Furthermore, the uniform composition and homogeneous structure promotes the generation of PbO\u003csub\u003e2\u003c/sub\u003e surface protective layer.\u003c/p\u003e"},{"header":"Experimental section","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Sample preparation\u003c/h2\u003e \u003cp\u003eFirstly, 2/3 of the required pure lead was added into the intermediate frequency furnace, where the temperature was rapidly increased the temperature to 500\u0026deg;C. After all the pure lead is melted, lead-silver, lead-calcium intermediate was introduced into the system. When all the alloys are melted, under the same conditions, the mechanical stirring device was adjusted to stir for 1min at different stirring speeds. Subsequently, NH\u003csub\u003e4\u003c/sub\u003eCl is added for slag removal, and the slag is fully fished out before casting. The Ag and Ca contents of the resulting alloy are measured to ensure that the final alloy keep the same content of each element, and the process is schematically shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFirstly, we cast the alloy with the same content of Pb-Ag-Ca at the mechanical stirring speed of 0r/min, 100r/min, 200r/min and 400r/min respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). According to the uniformity of the alloy cross-section, the overall uniformity of the alloy rises and then decreases with the increase of the stirring speed. The most uniform alloy can be obtained when the mechanical stirring speed is around 100r/min. The reason for this is the inhomogeneous composition of the melt obtained without stirring during melting. When the stirring speed is too high, the lead melt will be in full contact with the air to produce oxidation and a large amount of slag on the surface of the melt; at the same time, a large amount of oxide is generated inside the melt to make the cast alloy delamination. Therefore, we reduced the stirring speed interval and remelted the lead alloy for subsequent experiments.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe obtained alloys were numbered as samples 1, 2, 3, 4 and 5. The corresponding elemental contents and different stirring speeds are listed in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eElemental alloy content in different samples\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSample\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAg(%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCa(%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eStirring speed(r//min)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e100\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e150\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e200\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Metallographic oreparation\u003c/h2\u003e \u003cp\u003eSmall pieces of 10mm\u0026times;10mm\u0026times;10mm alloy are cut from the alloy blocks via wire cutting after rolling, which was then encapsulated with resin, exposing only the surface to be observed. The surface was sandpapered until no obvious rough scratches. The sample was then placed on the clean flannel of the polishing machine for polishing until the alloy surface displayed a bright mirror finish, and the polishing solution was used with 0.5 \u0026micro;m diamond spray polish. The use of corrosion solution (Acetic acid: hydrogen peroxide\u0026thinsp;=\u0026thinsp;4:1) will be bright surface corrosion out of the metallographic organization, and quickly wash away the residual corrosion solution with alcohol, dry with a hair dryer.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Mechanical properties test\u003c/h2\u003e \u003cp\u003eAfter observing the metallographic phase of the sample, the sample was put it on the flannel of the polishing machine to polish the surface corrosion layer. Then, the hardness was measured on the microhardness tester (HV-1000V). The tensile strength and plastic elongation strength of the material are tested by tensile test (UTM4304SLXY). After the specimen fails under tensile load, the percentage of the total elongation to the original length of the specimen is the elongation of the section. Since the lead alloy has no obvious yield point, the yield limit is taken as the stress value that produces 0.2% residual deformation.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Electrochemical tests\u003c/h2\u003e \u003cp\u003eThe comparative experiment mainly uses cyclic voltammetry, Tafel curves, anodic polarization curves, and AC impedance spectroscopy techniques to study the surface states of lead alloys in 150 g/L H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e, 50 g/L Zn\u003csup\u003e2+\u003c/sup\u003e solutions. The alloy properties were characterized by using the peak current peak potential of redox peaks, oxygen evolution overpotential, charge transfer resistance, and surface roughness. The electrochemical test adopts a standard three-electrode system, the test temperature is 35℃, the sample working area is 1.0cm\u003csup\u003e2\u003c/sup\u003e, the reference electrode is saturated mercurous sulfate (MSE): Hg, Hg\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/sat.K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e, and the auxiliary electrode is 1cm\u003csup\u003e2\u003c/sup\u003e platinum piece. The working electrode was connected to the auxiliary electrode by a saturated potassium sulfate agar salt bridge. The potential values measured electrochemically in the tests are both with respect to MSE.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.5 Accelerated corrosion test\u003c/h2\u003e \u003cp\u003eAccelerated corrosion tests were conducted in solution containing 150g/L H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e, 0.8g/L Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e: under current density 4000A/m\u003csup\u003e2\u003c/sup\u003e with corrosion time 120 h, where the anode size was 50 mm \u0026times; 30 mm \u0026times; 7.27 mm. The corrosion system adopts a liquid circulation system, the anode is a multi-polymer lead alloy plate prepared at different stirring speeds, and the cathode is a copper-plated titanium plate. Two pieces of each alloy were taken for accelerated corrosion experiments. After the corrosion test, one piece was taken to observe the surface morphology of the corrosion layer with SEM (TESCAN VEGA4) and XRD (Bruker D2); the other piece was boiled with a 1:1 mixed solution of NaOH and glucose to remove the oxide layer on the surface, and dried and weighed to observe the corrosion weight loss. The oxide layer on the surface of the other anode was washed off using a 1:1 boiling solution of NaOH and glucose, dried and weighed to observe the corrosion weight loss.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results and Discussion","content":"\u003cdiv id=\"Sec9\"\u003e\n \u003ch2\u003e3.1 Metallographic pictures\u003c/h2\u003e\n \u003cp\u003eThe metallographic images of the rolled Pb-Ag-Ca alloys prepared under different stirring speeds are shown in Fig. \u003cspan\u003e3\u003c/span\u003e. The grain boundaries of the rolled alloys are significantly elongated. There are dotted or long bright particles at the grain boundaries of different alloys, and these particles may be the intermetallic compound Pb\u003csub\u003e3\u003c/sub\u003eCa [\u003cspan\u003e12\u003c/span\u003e]. It can be seen from Fig. \u003cspan\u003e3\u003c/span\u003e, aggregation of intermetallic compounds is observed in the alloy matrix without stirring or with higher stirring speed (200r/min) (circled in Fig. \u003cspan\u003e3\u003c/span\u003ea and e). When the stirring speed is moderate (50 r/min\u0026thinsp;~\u0026thinsp;150 r/min), the intermetallic compounds are evenly distributed in the matrix without obvious aggregation.\u003c/p\u003e\n \u003cp\u003eThis phenomenon is ascribed to the fact that the intermetallic compounds in the unstirred are deposited at the bottom of the melt or float on the surface of the metal melt, leading to aggregation, while when the stirring speed is too high, the higher quality intermetallic compounds produced again due to the centrifugal action, which decreases the alloy uniform. The aggregation of intermetallic compounds causes the differences of the composition in various parts of the alloy, resulting in the decrease in its corrosion resistance and local corrosion during the working procedure. Alloys with uniform composition possesses higher corrosion resistance, resulting in uniform corrosion during the working procedure.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec10\"\u003e\n \u003ch2\u003e3.2 Hardness test\u003c/h2\u003e\n \u003cp\u003eThe hardness values of each alloy at five different positions and average hardness values for each alloy are shown in Fig. \u003cspan\u003e4\u003c/span\u003e. Among them, the bar chart represents the hardness values of five test points of different samples, and the line chart shows the change trend of average hardness. In Fig. \u003cspan\u003e4\u003c/span\u003e, the average hardness value of the alloy decreases with the increase of stirring speed, but the hardness values across the alloy become closer compared with sample 1. The similar value of the hardness after stirring originates from the uniformly distributed alloy elements. When stirring too fast or without stirring, the hardness of the produced intermetallic compound and its surrounding area is higher than other domain, and the area without intermetallic compound is close to that of pure lead, leading to the difference of hardness in samples. Therefore, the moderate stirring speed causes the more uniform distribution of intermetallic compounds in the matrix, leading to the more uniform and higher hardness.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec11\"\u003e\n \u003ch2\u003e3.3 Tensile measurement\u003c/h2\u003e\n \u003cp\u003eAdd tensile stress to both ends of the sample prepared at different stirring speeds and record the relationship between stress and strain. Figure \u003cspan\u003e5\u003c/span\u003e(a) shows the stress-strain curve of the alloy during stretching, and Fig. \u003cspan\u003e5\u003c/span\u003e(b) shows the variation of alloy strength values. From Fig. \u003cspan\u003e5\u003c/span\u003e, it can be seen that with the increase of stirring speed, The tensile strength and yield strength of the alloys show a trend of first increasing and then decreasing with the increase of the stirring speed. When the stirring speed reaches 100r/min, the alloy obtained the maximum tensile strength and the maximum yield strength of 40.73Mpa and 28.50Mpa, respectively. The optimal properties stem from the overall uniformity of the alloy. When subjected to tensile load, the entire cross-section of the alloy is uniformly stressed, resulting in an increase in strength. The unsuitable stirring speed leads to the poor internal uniformity of the alloy. When subjected to external loading, local stress is easily generated, and the tensile strength and yield strength of the alloy decrease.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec12\"\u003e\n \u003ch2\u003e3.4 CV investigation\u003c/h2\u003e\n \u003cp\u003eFigure \u003cspan\u003e6\u003c/span\u003e records the cyclic voltammograms of the Pb-Ag-Ca alloy samples with different microstructure. As observed, the profiles contain two main oxidation peaks and two reduction peaks regardless of whether stirring was performed during the preparation process, indicating that the microstructure shows little affect on the main reactions occurring on the substrate. The reaction represented by the oxidation peak a is: Pb\u0026thinsp;+\u0026thinsp;SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e-2e\u003csup\u003e\u0026minus;\u003c/sup\u003e=PbSO\u003csub\u003e4\u003c/sub\u003e [\u003cspan\u003e13\u003c/span\u003e]. Potential range [-0.8V, 1.0V] corresponds to PbSO\u003csub\u003e4\u003c/sub\u003e passivation range. Oxidation peak b represents the evolution of oxygen, the conversion of PbSO\u003csub\u003e4\u003c/sub\u003e to \u0026beta;-PbO\u003csub\u003e2\u003c/sub\u003e and the conversion of PbO to \u0026alpha;-PbO\u003csub\u003e2\u003c/sub\u003e. The reduction peak c is the reduction of PbO\u003csub\u003e2\u003c/sub\u003e to PbSO\u003csub\u003e4\u003c/sub\u003e. The higher the peak, the higher the content of PbO\u003csub\u003e2\u003c/sub\u003e in the surface film [\u003cspan\u003e14\u003c/span\u003e]. The reduction peaks d and dʹ are the reduction reactions of PbO and PbSO\u003csub\u003e4\u003c/sub\u003e to metallic lead.\u003c/p\u003e\n \u003cp\u003eIt can be concluded from Fig. \u003cspan\u003e6\u003c/span\u003e that with the increase of stirring speed, the intensity of oxidation peak b first increases and then decreases, and reaches the maximum value at 100 r/min, indicating that the anode activity is the highest at this time, and the surface generation of PbO\u003csub\u003e2\u003c/sub\u003e and oxygen evolution reaction are violent. This phenomenon is ascribed to the increasing surface roughness of the anode and the uniformity of the distribution of the intermetallic compounds in the alloy.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec13\"\u003e\n \u003ch2\u003e3.5 LSV investigation\u003c/h2\u003e\n \u003cp\u003eThe anodic polarization curve is one of the important methods to investigate the electrowinning process. The measured anodic polarization curve is subjected to Tafel analysis to obtain important reaction kinetic parameters such as oxygen evolution overpotential and apparent exchange current density. The potential values used for Tafel analysis are calculated by the equation below [\u003cspan\u003e15\u003c/span\u003e]:\u003c/p\u003e\n \u003cp\u003e\u003cem\u003e\u0026eta;\u003c/em\u003e\u0026thinsp;=\u0026thinsp;E\u0026thinsp;+\u0026thinsp;0.640\u0026thinsp;\u0026minus;\u0026thinsp;1.242 (1)\u003c/p\u003e\n \u003cp\u003ewhere \u003cem\u003eE\u003c/em\u003e(MSE) is oxygen evolution potential in the anodic polarization curve, 0.640 V(SHE) means the standard potential of MSE, 1.242 V stands for oxygen evolution reaction potential at 35\u0026deg;C in a mixed solution of 50 g/L Zn\u003csup\u003e2+\u003c/sup\u003e and 150 g/L H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e.\u003c/p\u003e\n \u003cp\u003eAfter processing the anodic polarization curve, it can be converted into the form of Tafel equation (\u003cem\u003e\u0026eta;\u003c/em\u003e\u0026thinsp;=\u0026thinsp;a\u0026thinsp;+\u0026thinsp;blg\u003cem\u003eJ\u003c/em\u003e), where \u0026eta;, a, b, J represent the oxygen evolution reaction overpotential, Tafel constant, Tafel slope, and electrode surface current density, respectively. By fitting a linear curve to the relationship between \u003cem\u003e\u0026eta;\u003c/em\u003e and lg\u003cem\u003eJ\u003c/em\u003e, the values of a and b can be obtained[\u003cspan\u003e16\u003c/span\u003e\u0026ndash;\u003cspan\u003e18\u003c/span\u003e]. When the value of \u003cem\u003e\u0026eta;\u003c/em\u003e is 0, the exchange current density \u003cem\u003eJ\u003c/em\u003e\u003csub\u003e0\u003c/sub\u003e can be obtained from the above equation. It can be known from the relevant electrochemical theory [\u003cspan\u003e19\u003c/span\u003e]. \u003cem\u003eJ\u003c/em\u003e\u003csub\u003e0\u003c/sub\u003e represents the degree of difficulty in the occurrence of reactions on the electrode surface, where a high exchange current density indicates that the polarization of the electrode is less likely, the reversibility of the electrode is improved, and the reactions on the electrode are more likely to occur.\u003c/p\u003e\n \u003cp\u003eFigure \u003cspan\u003e7\u003c/span\u003e (a) shows the anodic polarization curves of the alloy samples with different microstructure. With the increase of stirring speed, the oxygen evolution potential of anode decreases first and then increases. When the stirring speed reaches 150 r/min, the oxygen evolution potential at the current density of 50mA/cm\u003csup\u003e2\u003c/sup\u003e reaches the lowest value of 1.559V, and when the stirring speed reaches 200 r/min, the oxygen evolution potential reaches the highest value of 1.606V. Although the oxygen evolution potential of 100 r/min alloy is not the lowest (1.569V), it is also close to 1.559V. The logarithm of the current density log i for different alloys was then plotted against the overpotential \u0026eta;, and the relevant kinetic parameters were listed in the Table \u003cspan\u003e2\u003c/span\u003e.\u003c/p\u003e\n \u003cdiv\u003e\n \u003ctable id=\"Tab2\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv\u003eTable 2\u003c/div\u003e\n \u003cdiv\u003e\n \u003cp\u003eOxygen evolution kinetic parameters of alloy samples rolled at different stirring speeds\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ccolgroup cols=\"6\"\u003e\u003c/colgroup\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSample\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e0r/min\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e50r/min\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e100r/min\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e150r/min\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e200r/min\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ea\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.216\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.215\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.200\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.248\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.193\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eb\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.166\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.160\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.166\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.211\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.142\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eJ\u003c/em\u003e\u003csub\u003e0\u003c/sub\u003e(A/cm\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e5.101\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;8\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.661\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;8\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.436\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;8\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.260\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.190\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;9\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003eThe data in Table \u003cspan\u003e2\u003c/span\u003e indicate that with the increase of stirring speed, both a and b fluctuate in a small range, but both reach the lowest value when the rotation speed is 200r/min. The values of a and b represent the level of battery voltage and anode overpotential, respectively [\u003cspan\u003e18\u003c/span\u003e]. The smaller the values of a and b, the lower the total energy consumption, so the energy consumption is the lowest when the rotation speed is 200 r/min. However, the \u003cem\u003eJ\u003c/em\u003e\u003csub\u003e0\u003c/sub\u003e also reached the minimum value at this time, indicating that the reversibility of the electrode reaction was poor at this time, and the reaction on the electrode was more difficult.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec14\"\u003e\n \u003ch2\u003e3.6 Tafel curves\u003c/h2\u003e\n \u003cp\u003eFigure \u003cspan\u003e8\u003c/span\u003e shows the Tafel curves of alloys prepared at different stirring speeds. It can be seen from Fig. \u003cspan\u003e8\u003c/span\u003e that after adding the stirring process, the alloy curves all move forward towards the X-axis. The self-corrosion potential \u003cem\u003eE\u003c/em\u003e\u003csub\u003ecorr\u003c/sub\u003e and self-corrosion current density \u003cem\u003eI\u003c/em\u003e\u003csub\u003ecorr\u003c/sub\u003e values of the anode sample obtained from Fig. \u003cspan\u003e8\u003c/span\u003e are shown in Table \u003cspan\u003e3\u003c/span\u003e.\u003c/p\u003e\n \u003cdiv\u003e\n \u003ctable id=\"Tab3\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv\u003eTable 3\u003c/div\u003e\n \u003cdiv\u003e\n \u003cp\u003eSelf-corrosion potential and current density of electrodes at different speeds\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ccolgroup cols=\"6\"\u003e\u003c/colgroup\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSample\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e0r/min\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e50r/min\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e100r/min\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e150r/min\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e200r/min\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eE\u003c/em\u003e\u003csub\u003ecorr(V.MSE)\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-0.989\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-0.968\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-0.968\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-0.968\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-0.970\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eJ\u003c/em\u003e\u003csub\u003ecorr(A/cm2)\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.64*10\u003csup\u003e\u0026minus;\u0026thinsp;4\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.97*10\u003csup\u003e\u0026minus;\u0026thinsp;4\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.63*10\u003csup\u003e\u0026minus;\u0026thinsp;4\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.18*10\u003csup\u003e\u0026minus;\u0026thinsp;4\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.56*10\u003csup\u003e\u0026minus;\u0026thinsp;4\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003eAccording to Faraday\u0026apos;s law, the relationship between self-corrosion current density and metal self-corrosion rate is expressed as follows [\u003cspan\u003e18\u003c/span\u003e]:\u003c/p\u003e\n \u003cp\u003e\u003cem\u003eV\u003c/em\u003e\u0026thinsp;=\u0026thinsp;M\u003cem\u003eJ\u003c/em\u003e\u003csub\u003ecorr\u003c/sub\u003e/\u003cem\u003enF\u003c/em\u003e (2)\u003c/p\u003e\n \u003cp\u003ewhere \u003cem\u003eV\u003c/em\u003e is corrosion rate, M represents molar mass of metal, \u003cem\u003eJ\u003c/em\u003e\u003csub\u003ecorr\u003c/sub\u003e stands corrosion current density, n means metal valence, \u003cem\u003eF\u003c/em\u003e stands for Faraday constant. Theoretically, large anode corrosion potential means better corrosion resistance of the anode and less possibility of corrosion. High corrosion current density means that the higher the corrosion rate, the worse the corrosion resistance of the anode. As shown in Table \u003cspan\u003e3\u003c/span\u003e, the corrosion current density of 0r/min alloy is the highest (3.64\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;4\u003c/sup\u003e A/cm\u003csup\u003e2\u003c/sup\u003e), and the current density of 100r/min alloy is the lowest (1.63\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;4\u003c/sup\u003eA/cm\u003csup\u003e2\u003c/sup\u003e). The corrosion potential is the lowest value in the range of 50 r/min to 150 r/min (-0.968V).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec15\"\u003e\n \u003ch2\u003e3.7 AC Impedance Spectrum\u003c/h2\u003e\n \u003cp\u003eThe AC impedance spectra of Pb-Ag-Ca alloys at different stirring speeds measured in 50g/L Zn\u003csup\u003e2+\u003c/sup\u003e, 150g/L H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e electrolyte and equivalent circuit diagram of five kinds of anode fitting AC impedance are shown in the Fig. \u003cspan\u003e9\u003c/span\u003e. It can be seen from the curves that the AC impedance spectra of the four anode oxygen evolution reactions are similar, all of which are semicircles, so the charge transfer is still the control step.\u003c/p\u003e\n \u003cp\u003eThe relationship between the double-layer capacitance C\u003csub\u003edl\u003c/sub\u003e without solution compensation and the charge transfer resistance usually satisfies the following relationship[\u003cspan\u003e19\u003c/span\u003e, \u003cspan\u003e20\u003c/span\u003e]:\u003c/p\u003e\n \u003cp\u003e\u003cem\u003eQ\u003c/em\u003e \u003csub\u003edl\u003c/sub\u003e=(\u003cem\u003eC\u003c/em\u003e\u003csub\u003edl\u003c/sub\u003e)\u003csup\u003e\u003cem\u003en\u003c/em\u003e\u003c/sup\u003e [(\u003cem\u003eR\u003c/em\u003e\u003csub\u003es\u003c/sub\u003e)\u003csup\u003e\u0026minus;1\u003c/sup\u003e+(\u003cem\u003eR\u003c/em\u003e\u003csub\u003et\u003c/sub\u003e)\u003csup\u003e\u0026minus;1\u003c/sup\u003e]\u003csup\u003e(1\u0026minus;\u003cem\u003en\u003c/em\u003e)\u003c/sup\u003e (3)\u003c/p\u003e\n \u003cp\u003e\u003cem\u003eR\u003c/em\u003e \u003csub\u003es\u003c/sub\u003e stands for the resistance of the solution between the working electrode and the reference electrode, \u003cem\u003eR\u003c/em\u003e\u003csub\u003et\u003c/sub\u003e represents charge transfer resistance in the electrochemical reaction process charge transfer resistance, CPE refers to an element of constant phase element for the behavior of the electrode and electrolyte interface, which is often used to fit experimental data instead of capacitance. In addition, \u003cem\u003eC\u003c/em\u003e\u003csub\u003edl\u003c/sub\u003e can be used as a relative method to characterize electrode surface roughness, and its relationship with anode roughness (\u003cem\u003eR\u003c/em\u003eF) can be calculated by the following formula[\u003cspan\u003e21\u003c/span\u003e, \u003cspan\u003e22\u003c/span\u003e]:\u003c/p\u003e\n \u003cp\u003e\u003cem\u003eR\u003c/em\u003eF\u0026thinsp;=\u0026thinsp;\u003cem\u003eC\u003c/em\u003e\u003csub\u003edl\u003c/sub\u003e/\u003cem\u003eC\u003c/em\u003e\u003csup\u003e⁎\u003c/sup\u003e (4)\u003c/p\u003e\n \u003cp\u003eWhere \u003cem\u003eC\u003c/em\u003e\u003csup\u003e⁎\u003c/sup\u003e represents the capacitance reference value. For a smooth mercury electrode, \u003cem\u003eC\u003c/em\u003e\u003csup\u003e⁎\u003c/sup\u003e is 20 \u0026micro;F\u0026middot;cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e. The roughness values obtained from anodized films are often used to characterize the microscopic topography of electrodes [\u003cspan\u003e23\u003c/span\u003e]. Equivalent circuit fitting is performed on the impedance spectrum, and the fitting data are shown in the Table \u003cspan\u003e4\u003c/span\u003e.\u003c/p\u003e\n \u003cdiv\u003e\n \u003ctable id=\"Tab4\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv\u003eTable 4\u003c/div\u003e\n \u003cdiv\u003e\n \u003cp\u003eEquivalent circuit parameters of AC impedance spectrum of different anode materials\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ccolgroup cols=\"7\"\u003e\u003c/colgroup\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAnode specimens\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eR\u003c/em\u003e\u003csub\u003es\u003c/sub\u003e/(Ω\u0026middot;cm\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eR\u003c/em\u003e\u003csub\u003et\u003c/sub\u003e/(Ω\u0026middot;cm\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eQ\u003c/em\u003e\u003csub\u003edl\u003c/sub\u003e/(Ω\u003csup\u003e\u0026minus;1\u003c/sup\u003e\u0026middot;cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e\u0026middot;s\u003csup\u003en\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003en\u003c/em\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eC\u003c/em\u003e\u003csub\u003edl\u003c/sub\u003e/(\u0026micro;F\u0026middot;cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eR\u003c/em\u003eF\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0r/min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.931\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e17.17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.0195\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.873\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e10799\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e539\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e50r/min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.873\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e14.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.0278\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.840\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e13534\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e676\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e100r/min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.945\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e13.26\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.0286\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.859\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e15633\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e781\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e150r/min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.876\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e9.198\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.0235\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.859\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e12239\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e611\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e200r/min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.88\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e10.55\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.0234\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.884\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e13911\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e695\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003eThe EIS diagram shows that with the increase of the stirring speed, the diameter of the semicircle shows a decreasing trend, and reaches the lowest value when the rotational speed is 150 r/min. The charge transfer resistance \u003cem\u003eR\u003c/em\u003e\u003csub\u003et\u003c/sub\u003e also shows the same trend. When the rotational speed is 150 r/min, the \u003cem\u003eR\u003c/em\u003e\u003csub\u003et\u003c/sub\u003e value reaches the minimum, about half of the 0 r/min alloy. The smaller the \u003cem\u003eR\u003c/em\u003e\u003csub\u003et\u003c/sub\u003e, the smaller the charge transfer resistance, and the easier the electrochemical reaction occurs [\u003cspan\u003e24\u003c/span\u003e]. In addition, as the stirring speed increases, the surface roughness of the anode first increases and then decreases, and the \u003cem\u003eR\u003c/em\u003eF reaches the maximum value at 100 r/min. It is generally believed that the roughness is related to the oxygen evolution area of the oxide layer on the anode surface, and the larger the roughness, the more oxygen release area on the anode surface, and the easier the oxygen evolution reaction.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec16\"\u003e\n \u003ch2\u003e2.8 Accelerated corrosion investigation\u003c/h2\u003e\n \u003cp\u003eTable \u003cspan\u003e5\u003c/span\u003e reveals the accelerated corrosion weight loss rate of alloys after rolling. Apparently, with the increase of stirring speed, the anodic corrosion rate first decreases and then increases, reaching the lowest value at the stirring speed of 100 r/min, which is consistent with the Tafel test results.\u003c/p\u003e\n \u003cp\u003eThe corrosion mechanism is shown in Fig. \u003cspan\u003e10\u003c/span\u003e. In the melting process, with low stirring speed or without stirring, the intermetallic compounds and impurities are going to be deposited at the bottom of the melt, leading to the difference of the properties in the upper and lower surfaces of the alloy after the melt solidifies. The corrosion starts from the place where there are many impurities and compounds and penetrates into the interior. The moderate stirring speed results in the uniform microstructure of the alloys, therefore, uniform corrosion occurs on the surface of the alloy, and the corrosion rate slows down. As the there is a higher stirring speed, various impurities and substances produced at the edge and the center of the alloy, giving rise to different properties inside and outside the alloy. At the beginning, the corrosive solution penetrates into the interior of the substrate from the edge of each substance, and the oxide layer fall off seriously. After the external oxide layer is corroded, the internal pure lead is exposed to the working environment, and the corrosion resistance is greatly reduced. Then, the surface of another anode after corrosion was rinsed with first-grade water, and its surface corrosion layer was further observed by XRD and SEM.\u003c/p\u003e\n \u003cdiv\u003e\n \u003ctable id=\"Tab5\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv\u003eTable 5\u003c/div\u003e\n \u003cdiv\u003e\n \u003cp\u003eAccelerated corrosion weight loss rate after rolling of alloys with different stirring speeds\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ccolgroup cols=\"2\"\u003e\u003c/colgroup\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSample\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eWeight loss rate(%)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0r/min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.8557\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e50r/min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.6988\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e100r/min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.3632\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e150r/min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.4069\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e200r/min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.8129\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec17\"\u003e\n \u003ch2\u003e2.9 Surface morphology of alloy corrosion coatings\u003c/h2\u003e\n \u003cp\u003eThe surface morphology of the alloy prepared at different stirring speeds after accelerated corrosion is presented in Fig. \u003cspan\u003e11\u003c/span\u003e. With the increase of stirring speed, the uniformity and denseness of the anode surface film layer first increased and then decreased. The film denseness was best at the stirring speed of 100r/min, and then the film denseness and flatness gradually decreased. When the flatness of the film layer decreases and the surface pores increase, the electrolyte will pass through the surface pores of the film layer and contact with the substrate, and the film layer covering the surface of the substrate cannot play a protective role, which greatly reduces the corrosion resistance of the alloy. The result is consistent with the previous test.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec18\"\u003e\n \u003ch2\u003e2.10 XRD after anodic corrosion\u003c/h2\u003e\n \u003cp\u003eFigure \u003cspan\u003e12\u003c/span\u003e shows the X-ray diffraction pattern of the surface corrosion layer after anodic corrosion. In Fig. \u003cspan\u003e12\u003c/span\u003e, the anodic oxide films of each alloy are mainly composed of PbSO\u003csub\u003e4\u003c/sub\u003e(82-1854)、PbO(76-1796)、\u0026alpha;-PbO\u003csub\u003e2\u003c/sub\u003e(45-1416)、\u0026beta;-PbO\u003csub\u003e2\u003c/sub\u003e(41-1492), but the material content of each anode layer is different. The preferred growth directions of \u0026alpha;-PbO\u003csub\u003e2\u003c/sub\u003e are (111) plane and (110) plane, respectively, and the preferred growth orientation of \u0026beta;-PbO\u003csub\u003e2\u003c/sub\u003e is the (110) plane. With the increase of stirring speed, the peak intensity of \u0026alpha;-PbO\u003csub\u003e2\u003c/sub\u003e is always high and fluctuates in a small range, while the peak intensity of PbSO\u003csub\u003e4\u003c/sub\u003e first increases and then decreases the highest intensity of PbSO\u003csub\u003e4\u003c/sub\u003e is obtained until the stirring speed reach 100 r/min. The content of \u0026beta;-PbO\u003csub\u003e2\u003c/sub\u003e has no obvious change, but its peak intensity is higher for the alloy stirred at 100r/min.\u003c/p\u003e\n \u003cp\u003eThe reason is that the main reaction that occurs a few days before the formation of the anodic film is the conversion of PbSO\u003csub\u003e4\u003c/sub\u003e to \u0026alpha;-PbO\u003csub\u003e2\u003c/sub\u003e. At this time, the higher peak intensity of \u0026alpha;-PbO\u003csub\u003e2\u003c/sub\u003e is also reflects the better performance of the anode surface film. The high peak intensity of \u0026beta;-PbO\u003csub\u003e2\u003c/sub\u003e at the 100 r/min alloy anode is due to the large amount of PbSO\u003csub\u003e4\u003c/sub\u003e covering the alloy surface under this condition, which leads to an increase in the surface current density and potential in the region not covered by PbSO\u003csub\u003e4\u003c/sub\u003e, and due to the high oxygen evolution overpotential on the lead surface, the following two PbO\u003csub\u003e2\u003c/sub\u003e generation reactions occur first [\u003cspan\u003e25\u003c/span\u003e], leading to an increase in \u0026beta;-PbO\u003csub\u003e2\u003c/sub\u003e content.\u003c/p\u003e\n \u003cp\u003ePbSO\u003csub\u003e4\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;H\u003csub\u003e2\u003c/sub\u003eO-2e\u0026thinsp;=\u0026thinsp;=\u0026thinsp;PbO\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;2H\u003csup\u003e+\u003c/sup\u003e ԑ\u003csup\u003e0\u003c/sup\u003e=1.926v (5)\u003c/p\u003e\n \u003cp\u003ePb\u0026thinsp;+\u0026thinsp;2H\u003csub\u003e2\u003c/sub\u003eO-4e\u0026thinsp;=\u0026thinsp;=\u0026thinsp;PbO\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;4H\u003csup\u003e+\u003c/sup\u003e ԑ\u003csup\u003e0\u003c/sup\u003e=0.896v (6)\u003c/p\u003e\n\u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003eLead alloys with different microstructure was successfully prepared by melting method. During the whole preparation procedure, with or without stirring affects the microstructure of the alloy, to further affects the mechanical properties, electrochemical properties, and corrosion resistance properties of lead alloy anodes. Suitable stirring speed leading to a uniform composition and homogeneous microstructure, as the speed reaches 100r/min, the lead alloy possesses the highest tensile strength and yield strength compared with other samples, which originates from the homogeneous microstructure of the alloy. When stirring speed is too high, more second phases produced in the matrix, causes the bad properties. The decreased oxygen evolution potential of 30 mV and charge transfer resistance of 22.77%, and increased corrosion resistance of 1.49% also beneficial from the uniform composition and homogeneous microstructure of the alloy as the speed is 100r/min. Furthermore, the uniform composition surface of the lead alloy is conducive to generate a uniform and dense PbO\u003csub\u003e2\u003c/sub\u003e protective layer, reducing the damage of the electrolytic solution to the interior of the substrate and improving the corrosion resistance of the anode. Therefore, preparation process depends on the microstructure of the matrix, homogeneous microstructure plays a key role in improving the mechanical and electrochemical of the lead alloy matrix.\u003c/p\u003e "},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eCredit authorship contribution statement\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCheng Jiang:\u003c/strong\u003e investigation, conceptualization, data curation, formal analysis and writing original draft. \u003cstrong\u003eYingping Zhou and Ruidong Xu:\u003c/strong\u003e investigation, conceptualization and data curation. \u003cstrong\u003eBuming Chen\u003c/strong\u003e, \u003cstrong\u003eJun Guo\u003c/strong\u003e \u003cstrong\u003eand Yi Tao:\u003c/strong\u003e investigation, conceptualization, validation, writing-review \u0026amp; editing and supervision. \u003cstrong\u003eHui Huang\u003c/strong\u003e, \u003cstrong\u003eChao Gao and Zhongcheng Guo:\u003c/strong\u003e resources, funding acquisition, validation and supervision.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003cstrong\u003eDeclaration of Interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThere is no conflict of interest to declare.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis research is funded by the National Natural Science Foundation of China (No. 51564029, 22262017 and 51874154), The Technology Innovation Talents Project of Yunnan Province (No.2019HB111).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eH.T. 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Liangxing et al (2008), Anodization behavior on Pb-Ag-Ca-Sr alloy during zinc electrowinning, The Chinese Journal of Nonferrous Metals 18: 1342-1346. https://doi.org/10.3321/j.issn:1004-0609.2008.07.028\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Lead alloy, Mechanical stirring, Microstructure, Electrochemical property","lastPublishedDoi":"10.21203/rs.3.rs-4519418/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4519418/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eHomogeneous microstructure in lead alloy matrix plays an important role in improving its mechanical and electrochemical properties. In this work, different stirring speed provided during the melt casting of the alloy are tended to obtain lead alloys with different microstructure. The results show that proper stirring speed is beneficial for improving the overall homogeneity of the alloy, however, as the stirring speed is too high, plenty of second phase impurities and defects produced in the lead matrix, which possesses negative effect on the mechanical and electrochemical properties. The most uniform composition and homogeneous microstructure was obtained when the stirring speed is 100 r/min, which is conducive to the decrease of oxygen evolution potential of 30 mV and charge transfer resistance of 22.77%, and the increase of the corrosion resistance of 1.49%, and promote the generation of the uniform and dense PbO\u003csub\u003e2\u003c/sub\u003e protective layer.\u003c/p\u003e","manuscriptTitle":"Homogeneous Microstructure Improving the Mechanical and Electrochemical Properties of Lead Alloys by Stirring Treatment","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-06-18 06:50:20","doi":"10.21203/rs.3.rs-4519418/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"0e5740ab-0101-4c22-928d-4d429ffac224","owner":[],"postedDate":"June 18th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-09-19T13:45:31+00:00","versionOfRecord":[],"versionCreatedAt":"2024-06-18 06:50:20","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4519418","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4519418","identity":"rs-4519418","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}