What makes BP so corrosive?

[RobertSubnet]

Greetings all.

As we all know, black powder is very corrosive. Is it corrosive because it is hygroscopic, causing metal to rust or is there some other property (along with being hygroscopic?) that makes BP corrosive?

Here in Arizona it is not very humid-obviously.I wonder if black powder'scorrosive effect of attracting moisture is lessened here (due toless humidity)than say the swampsof Florida?

Not trying to get out of cleaning my MLs as soon as possible after shooting them, I just don't want to worry that I am not cleaning them soon enough. If that makes any sense.

~Robert

[Semisane]

sulfur + oxidation + H2O = sulfurous acid

[cayugad]

Also the corrosive powders like black powder and pyrodex contain, or actually whenignited leave various complex salt compounds in the barrel. These salts left after the ignitionattract moisture, and the moisture in correlation to the steel of the barrel will cause corrosion. Hot water and liquid dish soap will dissolve the salts. As does swabbing. Remove the salt and you protect the barrel. You can also use a black powder solvent. These solvents also neutralize the salts formed from the ignition of the powder. The gun oil application afterward again, further removes trace elements and helps block oxygen by forming a protect seal over the steel.

[lemoyne]

After black powder is burnt it has 57 different kinds of chemical salts in it, a bout the only thing I know of thats more corrosive is Pyrodex. Lee

[RobertSubnet]

So does the level of outside moisture (humidity) matter? Will the salts have less of a corrosive effect here in Arizona due to less moisture?

[cayugad]

ORIGINAL: RobertSubnet

So does the level of outside moisture (humidity) matter? Will the salts have less of a corrosive effect here in Arizona due to less moisture?

I am not a chemist, but I would theorize that the more moisture, the more reaction from the salts. The more reaction from the salts the faster the corrosive process would be. So in your case, in a dry non humid climate, you would slow down the rusting process clock, but not actually stop it.

[RobertSubnet]

Cayugad:

Ithink you are right and appreciate your thoughts. Was just wondering what exactly was it about BP that made it corrosive and if less moisture meant a slower rate of corrosion.

~Robert

[wabi]

In my limited experience the level of humidity has some effect, but not enough to really matter much. It's still a matter of hours - not days!
This past winter I shot a deer in the rain and didn't re-load or wipe the bore. I had the deer field dressed, tagged, and in the processor's cooler within a couple hours at most. As soon as I got home I cleaned the rifle and there was the brown color of rust on the first patch through the bore. No damage, but it was already starting to form!!!!!!!!!
In low humidity conditions you should be good for a few hours, but I always figure the sooner the better for cleaning!!!!!!!!

[lemoyne]

If you dont clean your gun itcan rust overnight, where it is humid like here on the down wind side ofGreers Fairy Lakeit just rusts faster and deeper. Lee

[rafsob]

Corrosionis a chemical process that is like an electric battery.You must have twoforms of conductors and an electrolite. The barrel metal is one conductor, the salts act as another conductor while the moisture isthe electrolite. Complete thecircuit and you have corrosion. Remove oneof theseitems and there could be nocorrosion.

Hope I said that right.