The preformed rods used in preformed tension clamps are primarily made of two materials: hot-dip galvanized steel wire and aluminum-clad steel wire. Each has its own advantages and disadvantages, and the choice depends on the specific application scenario. There are significant differences between the two regarding key performance indicators such as electrical conductivity, corrosion resistance, and weight.
Electrical Conductivity: Aluminum-Clad Steel Has a Clear Advantage
In terms of conductivity, aluminum-clad steel wire is far superior to galvanized steel wire. Standard galvanized steel wire has a conductivity of approximately 9% IACS, whereas aluminum-clad steel wire ranges from 14% to 40% IACS; notably, the resistivity of 20.3% IACS aluminum-clad steel wire is only about half that of galvanized steel wire. When subjected to short-circuit currents, galvanized steel strands experience a significantly higher temperature rise than aluminum-clad steel strands. Furthermore, the melting point of zinc is only about 420°C-far lower than aluminum's 660°C-making the galvanized coating more prone to peeling and failure at high temperatures.
Corrosion Resistance: Aluminum-Clad Steel Performs Better
Corrosion resistance is a key differentiator between the two materials. The dense aluminum layer on the surface of aluminum-clad steel wire naturally forms a protective Al₂O₃ film upon exposure to air, and it does not suffer from bimetallic electrochemical corrosion when in contact with aluminum conductors. In contrast, the zinc coating on galvanized steel wire can form a galvanic cell when in contact with aluminum wire in humid environments, thereby accelerating corrosion. Salt spray test results indicate that the corrosion resistance of aluminum-clad steel wire is approximately six times that of Class C galvanized steel wire (per US standards). In corrosive environments-such as coastal areas or regions with heavy pollution-transmission lines designed with galvanized steel wire typically have a service life of only about 15 years, whereas those using aluminum-clad steel wire can last over 30 years.
Weight and Mechanical Properties: Aluminum-Clad Steel Is Lighter
For the same specifications, aluminum-clad steel wire has a lower density than galvanized steel wire. This helps reduce the conductor's self-weight, making it particularly advantageous for long-span transmission lines. Regarding tensile strength, both materials meet line requirements; aluminum-clad steel wire combines the strength of steel with the conductivity of aluminum, representing a powerful synergy of properties. Selection Recommendations
Choose hot-dip galvanized steel for: standard atmospheric environments, lines with short spans, and projects requiring strict cost control. Galvanized steel is relatively inexpensive and meets basic operational needs in standard environments.
Choose aluminum-clad steel for: coastal areas with salt spray, regions with heavy industrial pollution, long-span crossings, OPGW (Optical Ground Wire) applications, and scenarios requiring high electrical conductivity and superior corrosion resistance. Aluminum-clad steel has completely replaced galvanized steel in OPGW manufacturing. Although aluminum-clad steel has a higher initial cost, its longer service life and lower power loss often make it more economical over the full lifecycle.
In summary: choose hot-dip galvanized steel for standard environments where cost-effectiveness is a priority; choose aluminum-clad steel for harsh environments and applications requiring a long service life.