Copper cathode is the final product of the copper refining and purification process, characterized by its exceptionally high purity. It is typically produced as flat sheets and serves as a key raw material in various copper-related industries. The significance of copper cathodes lies in their high purity and excellent electrical conductivity, which enable the production of high-quality wires and cables, uniform copper sheets, and superior copper alloys.
• Copper Purity (Cu): Higher than 99.99% in refined samples
• Appearance: Flat, smooth sheets with a thickness of about 6.0 to 6.5 mm
• Weight per Sheet: Approximately 100 to 104 kg (in standard dimensions)
• Standard Dimensions: Typically around 130 × 150 cm (length × width)
• Electrical Conductivity: Very high (over 99% IACS), comparable to global standards
• Crystal Structure: Uniform and free from internal voids or cracks, ensuring good mechanical quality
The chemical composition of a sample refined copper cathode, according to ASTM B115 standard, is presented in the following table:
| Element | Sample Refined Cathode (%) | ASTM B115 (%) |
|---|---|---|
| Copper (Cu) | 99.99 | ≥99.99 |
| Oxygen (O) | 0.03 | ≤0.04 |
| Silver (Ag) | 0.003 | ≤0.005 |
| Iron (Fe) | 0.002 | ≤0.005 |
| Lead (Pb) | 0.001 | ≤0.005 |
| Sulfur (S) | 0.001 | ≤0.005 |
| Bismuth (Bi) | 0.002 | ≤0.005 |
| Other Impurities (Total) | 0.01 | 0.01 |
The above table shows the chemical composition of a standard refined cathode sample. The values are defined based on international standards (including ASTM B115). As shown, the copper content is very high and impurities are within permissible standard limits.
• Wire manufacturing:
Used as the primary material for producing high-purity copper wires and cables.
• Sheet production:
Used for manufacturing copper sheets with high precision and good mechanical properties for electronics and construction industries.
• Alloying:
Pure copper is combined with other elements to produce important alloys such as brass (copper-zinc), bronze (copper-tin), and other engineering alloys.
• Tube manufacturing:
Used to produce special copper pipes and profiles for industrial applications and facilities.
• Electronics and electrical industries:
Used in the production of electronic motherboards, electrical connectors, and sensitive components requiring high conductivity.
Using high-quality copper cathode offers several advantages:
• High purity and low impurities:
Refined cathodes have very high copper content and minimal impurities, resulting in superior electrical and thermal conductivity.
• Improved final product quality:
Due to the uniform chemical composition, final products (wires, sheets, or alloys) have higher quality and better mechanical properties.
• Reduced production costs:
High-grade cathodes lead to lower waste, less equipment damage (due to lower corrosion), and improved production efficiency.
• Better process compatibility:
The uniform dimensions and properties of copper cathodes facilitate smoother processes like rolling, extrusion, and casting.
Electrolytic refining: In this method, after melting and casting copper anodes, the pure copper anodes are placed in a sulfuric acid solution. A direct current is applied, causing copper ions to migrate from the anode to the cathode plates, where they deposit as highly pure refined copper cathodes. This process yields cathodes with over 99/99% purity.
Leaching (solvent extraction and electrowinning): This method is mainly used for oxide ores and low-grade copper ores. The crushed ore is dissolved in acid, releasing copper into the solution. Through solvent extraction and electrowinning (EW), copper is separated and deposited on cathode plates. The final product of this method is known as leaching cathode.
• Purity and quality:
Refined cathodes have higher purity (≥99.99%) and lower levels of impurities such as oxygen, iron, and lead. Leaching cathodes usually have 99.90–99.95% purity, suitable for most applications.
• Mechanical properties:
While dimensional and structural differences are minimal, refined cathodes may have denser crystal structures due to the production method.
• Applications:
Both types are used in various copper industries. Refined cathodes are preferred in applications requiring highest purity and conductivity (e.g., electrical and electronics industries).
• Price:
Due to the more complex production process and higher purity, refined cathodes are approximately 5% more expensive than leaching cathodes.