Under standard LPI-175, which ground rod material is NOT acceptable?

Under standard LPI-175, galvanized steel is not an acceptable material for ground rods. This is primarily because galvanized steel, while it may resist corrosion to some extent, does not provide the same level of conductivity and longevity as other materials like copper, bronze, or stainless steel. Grounding systems need to ensure low resistance to ensure effective lightning protection and grounding, and thus it's crucial to use materials that maintain their conductive properties over time and are less susceptible to degradation.

Copper, bronze, and stainless steel are favored materials for grounding applications due to their excellent conductive properties and overall durability in various environmental conditions. These materials can effectively handle the electrical currents and the environmental stresses typically encountered in lightning protection systems.