Sodium hydroxide solution (NaOH) cannot be kept in aluminum containers because of a chemical reaction that occurs between the two substances.

Here's the breakdown:

* Aluminum is a reactive metal: Aluminum readily reacts with strong bases like sodium hydroxide.

* Reaction with sodium hydroxide: When sodium hydroxide solution comes in contact with aluminum, it forms sodium aluminate (NaAlO₂) and hydrogen gas (H₂).

* The chemical equation:

2Al(s) + 2NaOH(aq) + 6H₂O(l) → 2Na[Al(OH)₄](aq) + 3H₂(g)

* Consequences:

* The formation of sodium aluminate weakens the aluminum container, leading to corrosion and potential leaks.

* The release of hydrogen gas is flammable and can create a dangerous situation if not properly contained.

In short: The reaction between sodium hydroxide and aluminum produces a corrosive substance and a flammable gas, making aluminum containers unsuitable for storing sodium hydroxide solution.