Re: brass or steel stem?
Rust refers to the oxidation of iron so brass does not rust. It oxidizes just like iron, but the process is passivating. IOW the corrosion/oxidation layer that forms on brass reduces the permeability of oxygen to the underlying copper/zinc, protecting the brass from further oxidation. Rust can also be passivating depending on the conditions that it forms under but in most cases general corrosion of iron isn't (the red flaky stuff aka hematite or Fe2O3). Bluing of stainless steels is an example of passivating rust (magnetite or Fe3O4).
I would disagree that brass KMs are higher quality than the formed steel hollow stems. The assembly methods on both are mostly the same, the only difference being the pieces used. Brass stems are generally thought more highly of because they are heavier.
I've examined quite a few KMs and I've seen hollow stem KMs built better than brass stem KMs and vice versa. If there is one consistent thing I've noticed about KM stems it's that their quality isn't consistent. :P
edit: I should clarify that I meant real bluing of steel, not the half-assed done to make it look pretty bluing.
Last edited by foibled; October 9th, 2009 at 04:28 PM.