Aluminum cathode plates are widely used in zinc electrowinning, where the aluminum surface provides the base onto which zinc is deposited during electrolysis. Because the cathode plate sits at the center of that process, its dimensional accuracy, material quality, and the strength of the copper-aluminum bond all have a direct impact on plant performance. Before any cathode plate assembly leaves PRS, it goes through a structured inspection process — from raw material check through to final dimensional verification.
Raw Material Certification
Every batch of aluminum plate is supplied with a material certificate that we check against our specification before the material is approved for production. Depending on the supplier, this certificate may follow different formats, but it covers the same core checkpoints: material grade, tensile strength, elongation, Brinell hardness, and chemical composition (Al, Si, Fe content and other impurities). For our cathode plates, we typically work with H1070-grade aluminum, and each certificate is verified before the batch moves into production:
| Item | Detail |
|---|---|
| Specification | 1070×675×1020mm |
| Production Batch Number | 2026082601 |
| Material — Blade/Hanger Bar | 1070 |
| Tensile Strength | ≥120 MPa |
| Elongation | ≥4% |
| Brinell Hardness | ≥20 |
| Al Content | ≥99.7% |
| Si Content | ≤0.02% |
| Fe Content | ≤0.25% |
| Others | ≤0.03% |
On-Site Dimensional Inspection
A certificate confirms the material — it doesn’t confirm the part is dimensionally correct. Our QC team measures each cathode plate before shipment across the following dimensions:
- Hanger Bar (conductive beam) length
- Hanger Bar thickness
- Distance from the Hanger Bar end to the Lifting Lug
- Total distance between the two Lifting Lugs
- Lifting Lug height
- Lifting Lug width
- Cathode blade length
- Total cathode plate height
These measurements are recorded plate by plate to catch deviations that could otherwise cause misalignment issues downstream in the stripping line.
How the Copper-Aluminum Bond Is Made
The way the copper and aluminum are joined has a direct impact on the cathode plate’s conductivity and service life.
Conventional process: an aluminum-clad copper cast conductive head is joined to the aluminum beam by MIG welding. The copper and aluminum are only physically bonded during casting, not metallurgically — and because both metals oxidize readily, the bonding interface tends to oxidize during casting even with treatments like tin-plating, resulting in lower conductivity and weaker bond strength. Explosion welding, another common joining method, typically reaches a bond strength around 70 MPa.
PRS process: the copper-aluminum composite conductive head is first made by cold-press diffusion welding, then joined to the whole-body aluminum beam by friction-stir welding. Because this is a solid-state process, the material never melts, which avoids the defects associated with fusion welding and achieves a true metallurgical bond between copper and aluminum. The welding process also breaks up the oxide film at the copper-aluminum interface, resulting in a cleaner bond with better conductivity. This approach typically achieves a copper-aluminum bond strength above 100 MPa, and the forging action of friction-stir welding makes the weld zone denser than the base material — in the zinc electrowinning environment, this bond shows better conductivity and corrosion resistance than an argon-arc (TIG) weld.
What Counts as Acceptable vs. a Defect
Not every visible mark on a finished cathode plate is a quality issue, and it’s worth being upfront about what’s considered normal:
- Surface scratches on the plate: Since raw material plates pass through dozens of processing steps, minor scratches can occur. These are cosmetic and are not expected to affect service performance.
- Slight unevenness at the Cu-Al bonding area: Because our process bonds a solid block of copper (rather than only surface-bonding it via explosion welding), some slight unevenness can appear at the bonding area. This is a byproduct of the method used to improve conductivity and service life, not a sign of a weak joint.
- Particles or slight roughness on the black anti-corrosion coating: The coating is applied using a fluidized bed process, and minor particles or roughness can occur. This is not expected to affect the coating’s function.
In Summary
Each aluminum cathode plate we ship is checked against raw material certification and full dimensional inspection, with the copper-aluminum bonding area checked as part of that process. We also try to be clear with customers about which surface characteristics are cosmetic and which would actually indicate a problem, so that inspection reports are read accurately on the receiving end.
Beyond the Cathode Plate
Supplying and inspecting a quality cathode plate is only part of what we do. PRS also works with customers to:
- Improve the cathode zinc electrowinning process from steel ash, helping plants get more consistent output from this feedstock.
- Recover additional material from tailings, so material that would otherwise be lost stays part of the process.
- Set up cathode zinc stripping machines, helping speed up the stripping process on the production line.
