Galvanized steel is steel coated with a protective layer of zinc, primarily to prevent corrosion. This galvanization process does not turn the metal into an insulator; it remains an electrical conductor. Although the zinc coating acts as a sacrificial anode, corroding before the underlying steel, it does not interrupt the flow of electric current. Therefore, galvanized steel conducts electricity.
The Conductive Components
Galvanized steel’s ability to conduct electricity is rooted in the metallic nature of its two main components: the steel core and the zinc coating. Steel is an alloy of iron and carbon, characterized by metallic bonding. This bonding structure allows electrons to move freely throughout the material, which is the fundamental mechanism for electrical conduction.
The outer layer of zinc is also a metal and possesses conductive properties. Electrons can flow through the thin zinc layer and into the steel core without significant interruption, meaning the steel’s electrical properties largely dictate the overall conductivity of the galvanized product.
Comparative Electrical Resistance
While galvanized steel is a conductor, it is not highly efficient compared to metals chosen for electrical applications, such as copper or aluminum. The conductivity of steel, an iron-based alloy, is much lower than copper, often falling to about 12% to 15% of pure copper’s conductivity. Copper is the standard for wiring because its atomic structure allows electrons to move with minimal obstruction.
The higher electrical resistance in steel stems from the presence of iron and alloying elements that disrupt the flow of electrons. This resistance means that when high current is forced through galvanized steel, electrical energy is converted into heat. Thicker zinc layers can also increase the material’s overall resistance, as the coating itself has a slightly higher resistance than the steel core.
Real-World Applications and Safety
Galvanized steel is frequently used in structural and grounding applications where mechanical strength and corrosion resistance are more important than high current-carrying capacity. It is commonly used for grounding rods and structural components of utility infrastructure. The large cross-sectional area of these components compensates for the material’s lower conductivity when dissipating large, short-duration currents, such as a lightning strike.
When modifying or joining galvanized steel, safety precautions regarding the zinc coating are necessary. Heat generated during processes like welding or soldering causes the zinc to vaporize at its relatively low melting point of 419°C, which is well below the melting point of steel. This vaporization produces zinc oxide fumes, which are toxic if inhaled and can cause a temporary illness known as “metal fume fever.”
It is essential to remove the zinc coating from the area to be joined before applying high heat. Grinding or sanding the zinc off ensures both a safer working environment and a cleaner, stronger electrical connection. Ignoring this preparation can lead to weld defects and serious health risks from inhaling the toxic fumes.