system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do batteries sometimes leak acid and/or corrode when left in electronics for extended periods of time and what actually happens that destroys the electronic's leads? Acid eats it?
gpt
Alkaline batteries produce hydrogen gas inside the battery cell when recharged. This pressure pushes out a strong base (which is corrosive just like acid). This forms white fluffy stuff when it reacts with the air (Potassium carbonate).

Recharging batteries can be caused by two unequally charged batteries lined up in a row (set in series). This is why you should never use different brands of batteries together, or only replace some of the batteries.