When choosing the material for the “above ground” Lightning Conductor System, it is important to take into account the avoidance of any bimetallic corrosion. For example, one should avoid the installation of copper conductors over aluminium or steel cladding.
Galvanic corrosion – happens when there is a potential difference between dissimilar metals
When the materials are in contact in the presence of an electrolyte, corrosion occurs. One metal becomes the anode, the other the cathode. The anode will tend to go into solution and therefore corrode. The electrolyte can be water with impurities from the air.
In the instance of water run-off from copper – the water carries fine copper corrosion particles which, when they drip on to aluminium or zinc, may result in corrosion. The direct contact of the dissimilar metals is not required for corrosion to occur in such a case.