I've mentioned this before but it is worth mentioning again.
A lot of people point at Pyrodex and say, "Pyrodex has Potassium Perchlorate (a chloride) in it and it will eat the bore right out of your barrel!!!".
Many of these same people will praise Triple Seven saying, "T 7 sure is great. It doesn't cause any corrosion in my barrel at all."
They both seem to be right if the barrel isn't cleaned promptly after the gun is shot but they are leaving out one important thing.
Both Pyrodex and T7 contain Potassium Perchlorate.
Pyrodex contains 30% Potassium Perchlorate and T7 contains 30% Potassium Perchlorate.
(It is used to provide the oxygen in the powder).
The difference I notice is Pyrodex contains 8% sulfur while the T7 has none.
IMO, it is the sulfur that is causing the acids to form which can eat the barrel.
That said, it is VERY important to clean any muzzleloader after it has been shot using any muzzleloading powder.
All of the powders leave salts that can hasten the development of rust if they are not removed.