What material should be used for Tower Ground Bus Bars when not protected against precipitation runoff?

• A. Pure copper
• B. Aluminum
• C. Tin-plated copper
• D. Tinned copper

Answer: (D)

In outdoor grounding hardware where precipitation runoff can wash over the surface, you want a material that keeps its low resistance even when wet. Tinned copper has a protective tin coating that resists corrosion in such moist environments, so the ground path remains reliable and conductive over time. Pure copper would oxidize and increase resistance; aluminum is less conductive and more prone to galvanic issues with copper components. Tin plating on copper delivers the best combination of conductivity and weather resistance for a Tower Ground Bus Bar that's not protected against runoff.