In the copper electrolysis refining process, the anode plate,
as the core component of electrochemical reaction, directly
determines the current efficiency, cathode copper quality
and production cost. Traditional pure lead anode is gradually
eliminated due to low strength and easy corrosion, etc. Lead
alloy anode plate has become the mainstream choice for modern
copper electrolysis process by virtue of its excellent corrosion
resistance, electrical conductivity and mechanical strength. In
this paper, we will analyse the material characteristics,
manufacturing process, application advantages and maintenance
strategy of lead alloy anode plate to provide technical reference
for copper smelting enterprises.
I. The role and challenges of lead alloy
anode plate in copper electrolysis
Copper electrolysis refining is a key process to purify crude
copper (containing about 99% copper) to more than 99.99%
high-purity copper cathode by electrolysis. In this process,
the anode plate assumes multiple functions:
Conductive carrier: direct current is introduced into the electrolyte,
driving copper ions to dissolve from the anode and deposit at the cathode.
Reaction interface: When the crude copper anode is dissolved,
the impurity elements (e.g. As, Sb, Bi) form anode mud, and
the high purity copper ions enter the solution.
Structural support: Need to withstand electrolyte corrosion,
mechanical loads and thermal stresses to maintain geometric
stability over time.
However, traditional pure lead anodes face
the following problems:
Serious corrosion: electrolyte (H₂SO₄ concentration 150200g/L) erosion
leads to anode deformation and fracture, with a life of only 612 months.
High oxygen precipitation overpotential: anode side reaction
(2H₂O → O₂↑ + 4H⁺ + 4e-) consumes extra power, and current
efficiency is reduced to 90%~92%.
Impurity contamination: lead ions dissolve and mix with copper
cathode, reducing product purity.
Lead alloy anode systematically solves the above problems by
optimising the material proportion and structure design, and
becomes the core material for copper electrolysis to improve
quality and efficiency.
Material properties and optimisation
direction of lead alloy anode plate
1. Mainstream alloy system and performance comparison
Lead-calcium (Pb-Ca) alloy:
Calcium content of 0.03%~0.08%, improve creep resistance
and hardness, reduce anode deformation;
Current efficiency increased to 93%~95%, but corrosion
resistance still needs to be improved.
Lead-silver (Pb-Ag) alloy:
Silver content of 0.5%~1.0%, significantly reduce the overpotential
of oxygen precipitation (about 50mV), saving energy
consumption by 8%~12%;
Higher cost, suitable for high current density (>300A/m²) scenarios.
Pb-Ca-Sn-Ag (lead-calcium-tin-silver) multi-alloys:
Comprehensive advantages: calcium enhances mechanical strength,
tin (1%~2%) forms a dense oxide film, silver optimises conductivity;
Life expectancy of up to 2~3 years, optimal comprehensive cost
performance, market share of more than 60%.
2. Surface modification technology
Anodic oxidation treatment: PbO₂ protective layer is generated in
the electrolyte to reduce lead ion dissolution (<0.1mg/L).
Coating technology: titanium substrate plated with platinum, iridium
and other precious metals to further reduce the polarisation
voltage, but the cost limits its large-scale application.
Third, lead alloy anode plate manufacturing
process and quality control
1. Casting process
Raw material melting: high-purity lead (99.99%) and alloying elements
(silver ingot, calcium master alloy, etc.) are melted under inert gas
protection to prevent oxidation.
Continuous casting: vertical continuous casting machine is adopted, and
the cooling rate is controlled at 10~20℃/s to ensure grain
refinement and uniform composition.
Roll forming: the ingot is hot rolled (temperature 200250℃) for several
passes to the target thickness (815mm) to eliminate internal porosity.
2. Mechanical Processing and Inspection
Lug welding: copper conductive rod and anode plate are argon arc
welded or friction welded, joint resistance <5μΩ.
Geometrical precision: the flatness error of the plate surface is ≤1mm/m,
and the edges are chamfered to avoid stress concentration.
Non-destructive testing: X-ray flaw detection for internal defects,
ultrasonic thickness measurement to ensure uniformity.
IV. Application advantages and maintenance
strategy of lead alloy anode plate
1. Application benefit analysis
Reduced energy consumption: Oxygen precipitation overpotential is
reduced, and DC power consumption per tonne of copper is reduced
to 220250kWh (280320kWh for traditional process).
Improvement of copper cathode quality: lead ion dissolution is reduced
by 90%, and the purity of copper cathode is stable ≥99.995%.
Decrease in maintenance cost: life expectancy is extended to more
than 2 years, and replacement frequency is reduced by 50%.
2. Use and maintenance points
Electrolyte management:
Control Cl- concentration <50mg/L to prevent pitting corrosion;
Add Mn²+ (0.5~1g/L) to promote the formation of PbO₂ protective film.
Regular maintenance:
Check the thickness of anode plate every 3 months, local corrosion
>30% need to be replaced;
Mechanical cleaning of surface anode mud to avoid short circuit.
Failure warning:
Monitor tank voltage fluctuation (normal value 0.25~0.35V), sudden
increase >10% suggests anode corrosion or passivation.
V. Future trend: greening and intelligent upgrading
Material innovation:
Develop lead-graphene composite material to enhance conductivity
and corrosion resistance;
Biodegradable coating technology to reduce the risk of heavy metal pollution.
Process optimisation:
Pulse electrolysis technology to reduce anode polarisation and
extend service life;
Digital twin modelling to predict anode failure cycles for
preventive replacement.
Recycling Economy:
Efficient recycling of used anode plates (lead recovery rate > 98%)
to reduce resource dependence.
Conclusion
As the core material of copper electrolysis process, the performance of
lead alloy anode plate is directly related to the economic benefits and
environmental compliance of enterprises. With the continuous progress
of alloy design, manufacturing process and maintenance technology,
lead alloy anode plates are developing towards longer life, lower
energy consumption and less pollution. Copper smelting enterprises
need to combine their own process characteristics, scientific selection
and the establishment of a full life cycle management system, while
paying attention to the dynamics of new materials and intelligent
technology, in order to take advantage of the fierce competition
in the industry, and promote the realisation of the goal of green metallurgy.