I don't want to mess up todays science experiment, but it won't be steel. Steel would show rust. Stainless is to expensive for a production unit. I think you can safely assume it is alum. I would put some alum roof coating on it. I use dicor I believe. The white rubberized will reflect heat. I have a 04 and its alm. About that time they quit using it because it became to expensive. The rubber is cheaper and with creative marketing made to sound better . Some of the products are universal and will work on any surface.