I first encountered formic acid erosion/corrosion when our installed air conditioning and heat pump evaporator (indoor) coils began suddenly leaking refrigerant in 2008. These were not old coils either, and some had only been installed for a year when the issues arose. Most, however, were one to three years old and, unfortunately, outside of any manufacturers labor reimbursement warranties. When I heard from several manufacturers that the issue was formicary corrosion/erosion, I took a peak and the degradation of the copper tubing looked, for all the world, like the old ant farm tunnels. Funny, because in researching formic acid, I discovered some ant species excrete formic acid as a defense mechanism. That brought back the following memory.
When I was a young lad, I looked forward to my copies of Boys Life magazine. While the articles and stories of heroic events young boys had performed were great, it was the ads in the back that really captured my attention. X-ray glasses with the implication you could see through walls and objects, hovercraft kits you could build and lots of other cooler-than-life items. The one thing I did purchase was an ant farm. Being too tight with my limited monetary resources due to my $1/week allowance, and living out in the country, I simply dug up an ants nest to populate my ant farm.