When it comes to selecting a ground rod, engineers must avoid a one-size-fits-all approach. Different factors—material, soil resistivity, location, facility type, size, among others—play into the overall efficiency and service life of both the ground rod and overall grounding system. Below we provide key considerations for ground material selection and then compare the most common types.
Potential Factors to Ground Rod Material Selection
Once the soil and environmental conditions have been assessed, materials should be compared according to their individual performance in the following areas, and their compatibility with your unique situation.
Corrosion Resistance: Perhaps most influential to the service ground rod life of the ground rod, assess materials based on their inherent corrosion resistance to your soil conditions. Depending on salt, sulfate content or pH, different materials will work best.
Cost: The upfront cost of one ground rod material should not be compared directly to another material. Rather, the lifecycle value of two materials should be compared. If one rod is $20 and another costs $30 but the cheaper rod will only last one-quarter as long as the other, the more expensive rod is the more cost-effective choice.
Ease of Driving into the Earth: This relates to the material’s strength and the soil’s hardness. If a ground rod is bent or broken when driven into the ground, it may be more likely to corrode. Also, a damaged ground rod will less reliably provide the most direct path for electrical currents to travel and dissipate.
Copper Theft: Some have called copper theft an “epidemic” at different times, and ground rods are not exempt. Depending on your proximity to a population and local theft rates, consider the potential cost of replacing stolen copper ground rods and the immediate system inefficiency it would cause. Typically theft is related to conductors and other above-grade materials, but ground rods are not completely exempt.
Conductivity: As a ground electrode, a ground rod’s purpose is to provide a physical connection to the earth and provide the most direct path for a current to dissipate. Though conductivity differences are typically minimal between the most common materials, certain conductivity levels are required in specific regions and are important for providing that path to ground.
Comparing Common Ground Rod Materials
Copper-bonded and galvanized ground rods are the two most common types of ground rods throughout most of the world. In certain situations, stainless steel or solid copper ground rods may be installed to meet unique environmental conditions. What is commonly overlooked, however, is the life expectancy of the grounding electrode system compared to the life expectancy of the facility.
Copper-Bonded Ground Rods
Copper-bonded steel ground rods are manufactured through a continuous electro-plating process of copper over a steel core, resulting in a permanent molecular bond between the two materials. This should not be confused with copper-clad steel, as that method is no longer employed for ground rods due to a less reliable bond.