Copper is my choice for any air line installation. Easy to work with, won't rupture and make you mess your pants, and will not shower your work with rust flakes like black iron. We had black iron at work for years and the compressor was in a small room across the hall with no ventillation. Boy did that baby make water in the Florida humidity. We were going to use PVC to replace it but the safety office said no way!!! I have used copper and love it.
Be safe out there,