Zinc Pest? Do I call Terminix?
Seriously though. Almost all my locomotives are zinc castings. I’ve not noticed any of the boilers bubbling under the paint, YET. Is “zinc rot” something that can be prevented?
There is no stopping zinc pest. It' caused by impurities in the casting, and it's "baked in" to the casting.
All the manufacturers have had the issue at various times, I remember an MTH K-4 that had a swayback tender, it was quite literally falling apart. I've had a number of K-Line passenger car trucks that we're turning to dust. Of course, there's a more recent example, the JLC GG-1 side frames that have been talked about here recently.
If the casting doesn't have significant impurities, you will never see the issue. If the impurities are there, it's coming. Moisture and temperature can accelerate the issue, but there's no stopping it.