RE: What makes BP so corrosive?
 

Once I was bore brushing my old renegade after a few blasts of BP and the Kansas breeze carried some of the fouling powder into my eye. Burned like fire and thought I would go blind. (now if I can figure out which button I accedently pressed to make this Italics.)

RE: What makes BP so corrosive?
 

The one between the B and the U

Glad you didn't go blind!

RE: What makes BP so corrosive?
 

Black powder is corrosive even before you shoot. It's in the nature of the ingredients. Potassium nitrate (saltpetre, a salt) Sulphur (a mild acid in the presence of moisture), and Charcoal (attracts moisture and holds it because it is porous) This is a recipe for rust from the get go and after it is burnt it only gets worse.