What can powder do to internals of a Glock over time?

can powder ever corrode/rust the insides of a Glock even with time or do any other type of damage?????? come to think of it what makes ammunition Corrosive is it the powder they use or what????? i mean i shoot alot of that Tula ammo from russia it says on the box non corrosive but i i just got done doing a 100% Take down on my G17 and even cleaned the inside of the Firing Pin Channel Liner and no matter how many times i stuck Ballistol Soaked Patches in and pulled them back out they always come out Black so finally i just stopped and figured a little black residue can't hurt anything right??????? i mean let's say a few years from now there won't be any damage to it like rust/corrosion or any type of damage??????