Aluminium vessels should not be washed with materials containing washing soda because:

Aluminium vessels should not be washed with materials containing washing soda since washing soda reacts with aluminium to form soluble aluminate. Under normal circumstances, aluminum does not react with water, as an impermeable protective layer composed of aluminum hydroxide either forms within seconds or is already in place. With the addition of sodium hydroxide, the formation of a protective layer is prevented. With the production of aluminates Al(OH)4-, the amphoteric (capable of acting as either an acid or a base) aluminum hydroxide Al(OH)3​ goes in solution.The reaction is as follows:2Al + 6H​2O → 2Al(OH)3​ + 3H2​Al(OH)3​ + NaOH → Na+ + [Al(OH)4​]−