How do plastic-insulated copper busbars withstand the dual attacks of copper oxidation and electrochemical corrosion?
Publish Time: 2025-10-02
In modern electrical systems, copper busbars, as core conductors for high-current transmission, are widely used in distribution cabinets, switchgear, new energy power plants, and rail transit. However, copper is highly susceptible to environmental factors during long-term operation, facing the dual threats of oxidation and electrochemical corrosion. Once copper oxide or basic copper carbonate, commonly known as "verdigris," forms on the surface, it not only increases contact resistance and causes localized overheating, but can also lead to insulation failure and even short circuits. To address this challenge, plastic-insulated copper busbars have emerged. Through multiple protective mechanisms, they effectively resist copper oxidation and electrochemical corrosion, ensuring long-term stable and safe power transmission.
1. Causes and Dangers of Copper Oxidation
Copper reacts with oxygen in the air at room temperature to form a black layer of cuprous oxide or cupric oxide. Although this oxide film is initially dense, its conductivity is extremely poor, only 1/1000th that of pure copper, significantly increasing the resistance at the busbar connection points. When high current flows, localized temperature rise intensifies, forming a vicious cycle of "temperature rise - oxidation - increased resistance - further temperature rise," which can ultimately lead to connector burnout or carbonization of the insulation material. More seriously, in humid, sulfur-, or chlorine-containing industrial environments, the copper surface can undergo further electrochemical corrosion. When different metals come into contact in the presence of an electrolyte, a galvanic effect forms. While copper, acting as the cathode, does not dissolve directly, the pH change in the surrounding environment accelerates corrosion of other metals and generates conductive salts, increasing the risk of electrical creepage.
2. Plastic Insulation: Creating a Physical Isolation Barrier
The core protection of plastic-insulated copper busbars lies in their high-performance outer insulation layer. Made from materials such as polyvinyl chloride, cross-linked polyethylene, or thermoplastic polyurethane, this layer tightly wraps around the copper conductor through an extrusion or coating process, forming a continuous, dense physical barrier that completely isolates the copper from external air, moisture, and corrosive gases. High-quality insulation material offers excellent water vapor barrier properties and chemical stability. Even in high-temperature and high-humidity environments, it effectively prevents water molecules from penetrating the copper surface, fundamentally inhibiting oxidation. At the same time, the insulation layer has high dielectric strength and tracking resistance, preventing surface leakage and arcing.
3. Surface Pretreatment and Coating Technology: Enhancing Copper's Intrinsic Resistance
Before applying the insulation layer, copper busbars typically undergo rigorous surface treatment. First, cleaning removes oil, scale, and impurities to ensure a clean surface. Subsequently, tinning, silvering, or passivation can be used to further enhance corrosion resistance. Tin plating is the most common protective method. Tin not only provides excellent conductivity but also forms a dense tin oxide film in the air, preventing further oxygen diffusion. Furthermore, the electrode potentials of tin and copper are similar, minimizing the potential difference and reducing the risk of electrochemical corrosion. Silver plating is used in applications requiring high conductivity. Silver offers strong oxidation resistance and extremely low contact resistance, but it is more expensive and must be used in conjunction with an insulation layer to prevent sulfidation and blackening. Additionally, some high-end products use an environmentally friendly passivation solution to treat the copper surface, forming a nano-scale protective film to enhance corrosion resistance. This is then followed by an insulation coating for dual protection.
4. Structural Design and Installation Process: Eliminate Electrochemical Corrosion Induces
During system integration, plastic-insulated copper busbars must be designed to avoid conditions that can induce electrochemical corrosion. For example, copper-aluminum transition terminals or bimetallic composite plates must be used at multi-metal joints to prevent direct contact between dissimilar metals. Furthermore, the insulation layer should be chamfered or heat-shrunk at the ends to prevent electrolytic pathways between the exposed copper and surrounding metal brackets and bolts. During installation, the insulation layer should be kept intact to prevent cracks from bending or tightening. Specialized insulating caps or potting compounds should be used to seal the joints to further block moisture intrusion.
5. Long-Term Operation Verification and Maintenance Strategy
With these multiple protections, plastic-insulated copper busbars can operate stably over a temperature range of -40°C to +105°C and withstand salt spray tests for over 1000 hours. They are widely used in harsh environments such as coastal power plants, chemical plants, and subways. Regular infrared temperature measurement can monitor joint temperature rise and identify potential faults.
The plastic-insulated copper busbar utilizes a comprehensive strategy of "physical isolation + surface protection + structural optimization" to successfully build a solid defense against copper oxidation and electrochemical corrosion. This not only improves the safety and reliability of power systems but also extends the lifespan of equipment, making it an indispensable component in modern smart grids and high-end equipment. With the continued development of new materials and processes, its protective performance will continue to improve, providing even more lasting protection for power transmission.
