When brass electrical terminals are connected to dissimilar metal conductors, electrochemical corrosion caused by potential differences between the dissimilar metals is a key issue affecting connection reliability. Essentially, dissimilar metals form a galvanic cell in the presence of humid environments or electrolytes. The metal with the lower potential (such as aluminum) acts as the anode, accelerating dissolution. The zinc in brass (copper-zinc alloy) can also undergo dezincification corrosion due to the potential difference, ultimately leading to increased contact resistance, localized overheating, and even the risk of wire breakage. To avoid these issues, a systematic solution must be developed from three perspectives: material matching, process optimization, and protective design.
When directly connecting dissimilar metals, potential differences are inevitable. For example, the electrode potential difference between copper and aluminum can exceed 0.6V, making it highly susceptible to forming a corrosion cell in humid environments. In this case, copper-aluminum transition brass electrical terminals or bimetallic brass electrical terminals can be used. These terminals create a potential gradient through an intermediate layer (such as tinned copper or nickel-based alloy), keeping the potential difference within 0.2V and significantly reducing the corrosion rate. If conditions permit, prefer connecting conductors made of the same material, such as brass brass electrical terminals with copper conductors, to eliminate the potential difference at its source. In scenarios where mixed wiring is necessary, electrical regulations (such as NEC 110.14) must be strictly adhered to. Direct crimping of copper and aluminum into the same brass electrical terminal is prohibited; physical separation must be achieved through dedicated transition pieces.
Oxide layers and oily contaminants on metal surfaces increase contact resistance and accelerate localized heating. Before connection, thoroughly remove the oxide layer from the brass electrical terminals and the conductors using sandpaper or a cleaning solution to ensure the metal substrate is exposed. Tin plating is a cost-effective corrosion protection method for copper conductors. Tin's electrode potential (-0.14V) lies between that of copper (+0.34V) and aluminum (-1.66V), forming a protective layer that isolates air and moisture while improving contact performance. The crimping process requires strict control of pressure and cross-sectional area. When crimping with hydraulic pliers, ensure a cross-sectional area compression ratio of at least 90% to eliminate air gaps and intergranular segregation, thereby reducing localized corrosion caused by poor contact. For high-frequency vibration scenarios, friction welding or vibration diffusion bonding can be used. These techniques achieve a permanent connection through atomic-level bonding, avoiding the increased corrosion caused by loosening associated with traditional crimping.
After the connection is completed, a dual barrier of "physical isolation + chemical protection" is required. For physical protection, self-adhesive waterproof tape is first applied to block moisture, followed by heat shrink tubing and heat shrinkage to form a dense insulation layer. For humid or salt spray environments, epoxy resin or silicone rubber can be further potted to completely seal the connection. Chemical protection relies on conductive paste and anti-corrosion coatings. The metal powders (such as zinc and silver) in the conductive paste fill the connection gap, destroying the oxide film and forming a low-resistance path. The anti-corrosion agent in the paste neutralizes the electrolyte, slowing the corrosion process. Anti-corrosion coatings (such as epoxy paint and polyurethane) isolate oxygen and chloride ions, extending the life of the connection. Furthermore, the condition of the connection must be regularly inspected, and worn tape and conductive paste should be replaced every two to three years. For scenarios with frequent vibration or high loads, the inspection cycle should be shortened to one year.
By matching materials to eliminate potential differences, optimizing processes to block corrosion paths, and creating multiple barriers through protective design, we systematically address corrosion issues between brass electrical terminals and dissimilar metal conductors. This solution not only complies with electrical safety regulations but also significantly improves connection reliability, reduces the risk of equipment failure and fire caused by corrosion, and ensures the long-term stable operation of power systems.
