The paper posits that it’s due to low frequency electromagnetic induction in the tethers from the observatory operations, which is a pretty unique environmental factor.
Not galvanic action, apparently, but rather a sort of phase creep within the zinc as a result of putting some of it in an excitation state. They aren’t sure though, as there hasn’t been much research on the topic.
You have a mechanical failure that can’t be seen in the labs and isn’t reproducible at other sites. Suggests something environmental.
Like when natural fiber army gear starts dissolving in the jungles of Vietnam.
Could be direct action, or a side effect of a chemical in plant or animal detritus. Like pigeon poop on car paint.