Greetings, well, I refer to the AAA, but in the case of alkaline, everything has a useful life or called an hour of life, since it has leaks because the batteries work with active chemical reactions that do not last forever, also another important fact for the case of the alkaline ones because they have the following, a liquid electrolyte called potassium hydroxide, whose chemical component is very corrosive and can slowly wear out the battery case, when it is evident that it is completely discharged.

The reaction is when potassium hydroxide is released and it combines with oxygen in the environment.
KOH + H2O = K2CO3 is an alacylan salt, it is the powder that is evident in a battery that has already spent its hours of use.