Jim Liggett of Cornish, New Hampshire, asks:
“I am installing a lightning- ground system and plan to use a 5/8in rod extending at least 6in above my VHF antenna. Does it matter whether the pointed rod is solid copper or can it be copper-coated steel, as is often used for grounding rods on shore? If the steel rod will work equally well, is there a good way to keep the tip and the attachment point at the mast from corroding? Can you recommend a spray or galvanizing product?”
Tim Bartlett replies:
As an air terminal, a copper-coated rod should work perfectly well. Although steel is about ten times less conductive than copper, the rod makes up for it by having 10 times more cross-sectional area than the 4 AWG copper that is usually recommended as the minimum for the main conductor in a lightning protection system.
My bigger concern is that a copper-coated steel lightning rod installed on an aluminum mast might create quite a galvanic cocktail of different metals, and in a place where you are least able to keep an eye on what is happening.
The copper doesnt need protection against corrosion. Rather it is the aluminum thats at risk. Adding a bit of zinc-rich paint to the mixture could give some added protection, but I dont expect it will make that much difference. My preferred solution would be to install an aluminum air terminal. Its not that much more expensive, its only marginally less conductive than a copper unit, but it is much better than steel. Best of all, it poses no galvanic threat to your aluminum mast.