How do copper-aluminum busbars solve the problem of electrochemical corrosion in dissimilar metal connections in power systems?
Publish Time: 2025-09-03
In modern power systems, copper-aluminum busbars serve as the core carrier of power transmission, carrying high currents and ensuring high reliability. Copper and aluminum, two commonly used conductive materials, each have their own advantages: copper boasts high conductivity and excellent mechanical strength, but is also costly and heavy; aluminum offers low density and a lower price, making it suitable for long-distance and large-span applications, but suffers from slightly lower conductivity and is susceptible to oxidation. In practical projects, copper and aluminum busbars are often connected to achieve device interface compatibility or optimize cost structures. However, copper and aluminum are dissimilar metals, making direct contact in humid or polluted environments highly susceptible to electrochemical corrosion (also known as galvanic corrosion). This increases contact resistance, heats the joint, and in severe cases, can even cause power outages.1. Causes of Electrochemical Corrosion: Metal Loss Driven by Potential DifferenceElectrochemical corrosion essentially occurs when two metals form a galvanic cell in the presence of an electrolyte (such as moisture, salt spray, or dust). When they come into direct contact and are exposed to humid air, the aluminum, acting as the anode, loses electrons at an accelerated rate, undergoing an oxidation reaction to produce loose aluminum oxide, while the copper, acting as the cathode, remains protected. This process not only consumes the aluminum, but the resulting oxide film is also highly resistive, leading to poor contact and localized temperature rise at the joints. This in turn triggers a vicious cycle that can ultimately lead to joint burnout.2. Material Optimization: The Innovative Structure of Copper-Aluminum Composite BusbarsTo fundamentally address corrosion issues, copper-aluminum composite busbars are widely used in modern power projects. These busbars utilize advanced metallurgical bonding processes (such as friction welding, flash welding, explosive welding, or cold pressing) to firmly bond the copper and aluminum layers together into a single-piece structure. Key to this is the specialized treatment of the composite interface to form a stable transition layer, effectively blocking electrolyte penetration. Furthermore, the copper is typically exposed only at the connecting ends, where it interfaces with the copper terminals, while the main body is aluminum. This prevents large-scale direct contact between the copper and aluminum, significantly reducing the risk of galvanic corrosion.3. Transition Connectors: Application of Specialized Copper-Aluminum JointsIn applications where composite busbars are unavailable, copper-aluminum transition joints (also known as copper-aluminum transition terminals) are commonly used. These joints have one copper end for connecting to copper busbars or equipment terminals, and the other aluminum end for connecting to aluminum busbars. The two are connected in the factory by welding or mechanical crimping, and the mating surfaces are treated with special treatments (such as tinning, silvering, or coating with an antioxidant compound grease). This coating not only improves the electrical conductivity of the contact surface but also isolates the copper and aluminum from direct contact, preventing electrolyte intrusion. During on-site installation, only the copper and aluminum wires need to be crimped separately, eliminating the need for direct connection of dissimilar metals on-site and ensuring a reliable and corrosion-resistant connection.4. Surface Treatment and Protective MeasuresAfter the connection is completed, further protective measures are essential. Common methods include:Applying electrical compound grease: Applying a specialized antioxidant conductive paste (such as zinc- or aluminum-based compound grease) to the copper-aluminum contact surface fills microscopic gaps, preventing air and moisture intrusion while maintaining good electrical conductivity.Sealing and Insulation: Use heat shrink tubing, insulation boxes, or sealant to fully enclose the connection points, isolating them from external moisture and contaminants and forming a physical barrier.Environmental Control: Maintain a dry and ventilated environment in the distribution room or bus duct. Install a dehumidifier if necessary to reduce the presence of corrosive media.5. Standardized Construction and Regular InspectionEven with high-quality materials and workmanship, improper installation can still lead to corrosion. Surface cleaning (removal of oxide film), crimping force control, and connection sequence must be strictly adhered to standards. Additionally, regularly checking connector temperature with an infrared thermometer or monitoring electrical performance with a contact resistance tester can help identify potential fault points and prevent them from occurring.The use of copper-aluminum busbars in power systems is unavoidable, but the problem of electrochemical corrosion has been effectively controlled through the use of a combination of technologies, including copper-aluminum composite busbars, specialized transition joints, surface protection, and standardized construction. These solutions not only ensure efficient and safe power transmission, but also strike a balance between cost and performance, providing solid support for the reliable operation of modern power grids.
