It's set in a forest, in which the sword has been exposed to the elements and is starting to rust. I'm trying to not have too little corrosion, but also not have so much that it becomes gaudy or unrecognizable. I've found it rather tricky trying to strike that balance.
Then there comes the trouble of making the rust itself look convincing. I've been operating mostly off of the methods found in Andrew Price's Blender Guru rust tutorial.
I also mapped the smaller specs by running a bare metal texture through a color ramp.
In addition, I've tried tinting the whole blade texture a slight rust-color- though I'm not certain about that working.
The details are in the nodes (for the blade only, since I don't have the permissions for more pics.