Although aluminium lies above hydrogen in the electrochemical series, it is quite stable in water and air. Why ?

Explanation

Aluminium is a highly reactive electropositive metal. In presence of water and air, a thin layer of aluminium oxide `(Al_2O_3)` forms over the metal surface. Consequently, this protective layer prevents further reaction of aluminium with water or air. So, aluminium is quite stable in water and air, in spite of being situated above hydrogen in the electrochemical series.