Question

how does the usage of aluminium in paints prevent rusting?

Answer 1

Actually, aluminium paint at first reacts faster to form aluminium oxide(Al₂O₃​) which is quite hard, and is used on abrasive sheets. It tends to corrode heavily if it's in contact with Oxygen. But at the result, Aluminium oxide builds a very thin and robust layer (passivation layer) which is impermeable to water and oxygen and that protects the metal from further corrosion or degradation or rusting.