purpose: form stronger, thicker layer of aluminium oxide to improve corrosion resistance

components in cell set up

electrolyte: dilute H₂SO₄(aq)

cathode: Pt/graphite electrode

anode: Al electrode

species present: H⁺, SO₄^2-, H₂O

@ anode, H₂O oxidised; 2H₂O(l) -> O₂(g) + 4H⁺ + 4e^-

O₂(g) reacts w/ Al anode to form thick porous layer of oxide

2Al(s) + 3/2O₂(g) -> Al₂O₃(s)

OVERALL anode eqn

2Al(s) + 3H2O(l) -> Al₂O₃(s) + 6H⁺ + 6e^-

@ cathode, H+ reduced; 2H⁺ + e^- -> H₂(g)

OVERALL eqn

2Al(s) + 3H₂O(l) -> Al₂O₃(s) + 3H₂(g)

Spell: H2 Chemistry 21 - Electrolytic cells