No, aluminum will not rust if left outside. Unlike other metals, aluminum possesses a protective oxide layer that naturally forms on the surface which prevents corrosion. Moisture and air cannot penetrate this protective layer and inflict harmful effects. Even in the rain, sun, or salty winds, aluminum remains strong. Though it loses some luster, it does not rust or deteriorate over time. Because of these properties, aluminum is favorable for outdoor uses like cladding, ceilings, and building facades.
