Sweat is a problem, because it does contain salt, but I do not see this being a problem for a long walk with a sweaty T-shirt, especially with the AK.
Mikhail Kalashinkov's design is built to design the worst mud, the worst weather, the worst of the worst. Kalashinkov's beauty of design isn't the most accurate, but it might be the most durable assault weapon on the planet.
I would say with the bare basic of firearm maintenence, you should be fine for many years to come.
you can get ammo....