Independant Tests?? - 2 come to mind: 1 run in a British magazine and one done by a local shooter here: They were pretty much the same: 3 pieces of clean - degreased steel: 1 a control; 1 with a quantity of Black Powder burnt on it and the 3rd with a similar quantity of Pyrodex burnt on it. The pieces were then left to see what would happen- I can't remember the time intervals at which the local guy checked the pieces but at the end the control had a light specking of rust as you would expect from unprotected steel; the BP sample had an even coat of light rust with no pitting; Pyrodex had caused flakey rust with deep pitting. As for temperature my reading leads me to believe that BP burns at 1300 - 1500 degrees C and Pyrodex at about 4500 Degrees. As I said; fastidious cleaning will help if you have to use Pyrodex.