difference in two types of ground rods, copper and galv

[Adnan Hasan]

What is the difference

The resistance of the electrolyte, or soil, is one of the most important factors that affects the flow of current associated with galvanic corrosion. By Ohm's law, we find that the lower the resistance of the electrolyte, the larger the corrosion current. Consequently, the lower the soil resistivity, the greater the galvanic corrosion.
Galvanized steel rods would not be used in actual grounding because the zinc will corrode away and expose bare steel, which would rust. Instead we would use a zinc anode, which consists of a small steel core embedded in zinc. These come in many sizes, but the sizes that are best suited for a ground rod are designated by the American Zinc Institute as AZI-2-30 and AZI-4-60. The first number is the cross-sectional area in square inches, and the second number is the weight in pounds. Each is 5 ft (1.52 m) long.
(source: standard IEEE 142, 1999, section 4.4.5)