When changing the batteries in my programmable Honeywell MagicStat 5/2 thermostat, I noticed a thin layer of dry blue chalk-like deposit on one of the negative terminals in its two-AA battery compartment.
No leakage from the AA alkaline battery, no deposit on the other negative terminal, thermostat at least 20 years old.
The deposit came off fairly easily- most with a Q-Tip, the rest I scraped off with a small knife.
Never seen a blue deposit before- wonder what it i
Copper oxide? But the rest I can't even guess at.
Alkaline batteries leak...it's what they do. When you become sick and tired of cleaning up battery compartment messes, give rechargeable Eneloops a shot. I've got some from 2011 that are still going strong.
Google says potassium hydroxide is the electrolyte and the negative electrode is zinc and the positive electrode is manganese dioxide. Neither carbonate is blue and maybe it is from a metal in the contacts.
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