# Does the chemical in an alkaline battery make battery leaks unavoidable?

Battery leaks was an issue in the 80s and 90s, and since quality and innovation is constantly improving, I thought battery leak might be slowly going away. But I found that even nowadays, name brand alkaline batteries still leak after a while, even if originally concealed in a tight package of the metal shell. Is it true that the chemical in an alkaline battery inherently expands in volume over time, and make the alkaline battery leak issue unavoidable?

• I'm betting that the alkaline solution just slowly eats the casing. – Ben Norris Aug 17 '12 at 16:06
• Nope, it eats zinc electrode. Wikipedia article about alkaline batteries has good discussion on the subject – permeakra Aug 17 '12 at 16:59
• @permeakra The wikipedia article is not bad, but one key feature is missing: Where is the KOH? Is it mixed with the Zn? Is it mixed with the manganese (II) oxide? KOH reacts with amphoteric oxides, like manganese (I) oxide and zinc oxide, which form as the battery discharges. I'm not sure where the hydrogen gas mentioned comes from; hydrogen usually forms in acidic redox. I would guess that water forms, and expands and/or vaporizes. – Ben Norris Aug 18 '12 at 12:09
• $KOH$ is electrolyte here, it has to have contact with both $MnO_2$ and $Zn$ . $Zn$ slowly reacts with solutions basic enough, the reaction is $Zn + 2KOH + 2H_2O = K_2[Zn(OH)_4] + H_2$. The reaction is slow and may be slowed even further by slowing diffusion in electrolyte solution, but not stopped. When battery is discharged (but not self-discharged), the reaction is different and no hydrogen produced. When battery cannot be discharged externally (too low voltage to give some current) it still can self-discharge and hydrogen produced will tear case apart if any Zn remains in battery. – permeakra Aug 18 '12 at 14:33
• @permeakra That is a pretty good explanation. You should turn it into an answer. – Ben Norris Aug 19 '12 at 13:48