Hot Stick

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 doesn’t need protection against corrosion. Rather it is the aluminum that’s at risk. Adding a bit of zinc-rich paint to the mixture could give some added protection, but I don’t expect it will make that much difference. My preferred solution would be to install an aluminum air terminal. It’s not that much more expensive, it’s 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.

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