Computer harddrive pieces

I scavenged a few old harddrives for their strong magnets and realized that most pieces of a drive are not steel. Are they all aluminum? In particular, the housing is fairly heave and magnet does not stick to it. It seems to be all metal but it's covered usually by some sort of black coating. Not sure if it's some type of paint, or insulation or what. Anyhow, if I take it to a recycler, is this going to be taken at the same rate as cast aluminum? Or the same as soda cans? or what?

Thanks!

If a magnet does not stick to it, it is likely aluminum or stainless steel. There are several ways to figure out which, including relative weight, but what I do is this - use a grinder. If it throws sparks, it is stainless steel; if no sparks, it is aluminum.

(Caveat) I have no experience scrapping computers.

Our scrap yard takes it in as cast aluminum.