I have a Schwinn Crisscross, like this: http://www.bikehounds.ca/wp-content/...3482-Large.jpg

via google, I found out that the frame is probably aluminum. But, what are the seat post and stem made out of?

I ask, because my bike is rusting and it needs some work. I'm trying to decide between bluing/blacking, auto painting, or electroplating (if I can make electroplating affordable!) in various areas.
But, I need to know what kinds of metals they are to make those decisions.

Thanks for your help!