Study On The Internal Stress Formation And Properties Of Oxide Film On Lead Anode

Lead substrate anodes are widely used in industrial hydrometallurgical processes,such as electroplating and electroplatic filed.But internal stress of anodic matericals surface are easily changed in the process of electric filed carried out,leading to the formation of the porous and loose oxide film,and even their break from lead substrate.This has a remarkable effect on solution compostion and reductive product quality.So it presents theoretical and practical significance that in the internal stress and properties of oxide film on lead anode are investigated in details.In addition,this contributes to energy saving and the design of good andic materials.In this paper,sulfate ion,chromium ion or chloride ion solution is used as electrolyte that is common in hydrometallurgy processes;the anode is the pure lead,and carried out of the research of anode surface corrosion process.Study on the internal stress formation and properties of oxide film on lead anodes electrolyzed in different solution.The main results are as follows:（1）The study on the internal stress formation and properties of oxide film on lead anode in electrolyte with different pH shows that:In SO₄^2-solution,the lead anodic film is mainly composed of Pb,PbO,PbSO₄,and Pb₃O₄.pH has less impact on the oxide film stress.The corrosion resistance of the oxide film decreases and then increases,the corrosion resistance of the oxide film is the weakest at pH=5.Anode showed n-type semiconductor with the range of potential-0.4V～0.7V,and anode performance of p-type semiconductor with the range of potential 0.7V～1.2V when pH=1 and 5.Anode is insulated at pH=3,and the anode is n-type semiconductor at pH=7.In chromium ion solution,the main component of the oxide film isPb and PbO,and the oxide film presents obvious cracks at pH=5.PbO,Pb₃O₄ and PbCrO₄ have impact on the changes of oxide film stress.The corrosion resistance of the oxide film becomes weakenafter strengthening with the increase of pH,and corrosion resistance of the oxide film is strongest and lead easily oxidized PbCrO₄ at pH=5 Anode shows n-type semiconductor with the range of potential-0.4V～-0.2V,andanode presents p-type semiconductor with the range of potential-0.2V～1.2V when pH=1.Anode is n-type semiconductor with the range of potential-0.4V～0.7V,andp-type semiconductor with the range of potential0.7V～1.2Vat the other pH.In Cl^-solution,the main component of the oxide film is Pb,Pb（OH）Cl and PbCl₂.The morpHology of the oxide film changed from flocculent into needle and again into lump with the increase of pH.Pb（OH）Cl has a greater impact on the stress of oxide film,the stress is the maximum when pH=5.When the pH = 1,7,the corrosion resistance of the oxide film is stronger than the pH = 3,5,and the anodic oxidation film exhibits n-type semiconductor.（2）The study on the internal stress formation and properties of oxide film on lead anode in electrolytic with different current densities shows that:In SO₄^2-solution,with increase of the current density,the main component of the oxide film changed from the base lead and PbO_n（1<n<2）to Pb₅O₈ and 2PbO₂·PbSO₄.Thedensity of oxide film increases with the current density increasing.Pb₅O₈ and PbSO₄ present compressive stress,and PbO/PbO₂ present stensile stress,but the current density has less impact on theinternalstress.The corrosion resistance of the anodic film reduced with the current density increasing,andPb/PbSO₄ becameeasy.Anode shows n-type semiconductor with the range of potential 0V～0.6V,andp-type semiconductor with the range of potential 0.6V～1.2V.In chromium ion solution,the corrosion products of oxide film are mainly Pb and PbO·PbCrO₄,the oxide film tends to be smoothwith the current density increasing,and corrosion resistance of the oxide film decreased,the corrosion resistance of oxide film is the lowest when the current density is 0.4 A/cm².PbCrO₄has effect on the stress ofoxide film.Anode presents n-type semiconductor with the range of potential-0.4V～1.0V,andp-type semiconductor with the range of potential 1.0V～1.2 V.In Cl-solution,the component of the oxide film is made up of Pb,Pb（OH）Cl and PbCl₂,oxide film gradually grows from the granular to massive,and the density ofoxide film decreased.The current density has little effect on the stress of oxide film,andanode isn-type semiconductor.The anode capacitance is controlled by PbO with the range of potential-0.4V～0,and PbCl₂ with the range of potential 0V～1.2V.（3）The study on the internal stress formation and properties of oxide film on lead anode in electrolyte with different oxidation time shows that:In SO₄^2-,chromium ion or Cl^-solution,the diffraction peaks oflead substrate occurred mainly in the early oxidation,and decreased withoxidation time increasing,the diffraction peaks gradually increased when the oxidation time is above 10min.In SO₄^2-solution,the stress changed from compressive stress to tensile stress,the compressive stress ofPbSO₄ increased as oxidation time extended,and the corrosion resistance of the anodic film reduced after increased,when the oxidation time is 20min,the corrosion resistance of the anodic film is the worst.Anode presents n-type semiconductor,the anode semiconductor shows two donor state when the oxidation time are 5min and 20min,anode capacitance is controlled by PbO with the range of potential-0.4V～0.1V,and PbO₂ with the range of potential 0.1V～1.2V,anode semiconductor status doesn’t change at 1min and 10min.In chromium ion solution,PbO and PbCrO₄ present tensile stressin the initial oxidation time,butPbCrO₄ converts to compressive stress when the oxidation time prolonged,andthe corrosion resistance of the anodic film increased,and the corrosion resistance of the anodic film is the strongest when the oxidation time is 20min.Anode presents n-type semiconductor,the anodic film conductivity decreased after enhanced with the oxidation time increasing,and the anodic film presents the strongest conductivity when the oxidation time reached 20min.In Cl^-solution,tensile stress of PbO significantly increases with the role ofPb（OH）Cl,andthe corrosion resistance of the anodic film reduced afterincreased.Anode presents n-type semiconductor,the anode semiconductor has two donor state in the initial oxidation time,and anode capacitance is controlled by PbOwith the range of potential-0.4V～0V,and PbO₂ with the range of potential 0V～1.2V.