I used to carry a S&W 625 Mountain Gun while deer hunting and riding my ATV out in the boonies. The holster is a Bianchi nylon flap holster on a nylon belt with cartridge loops. I'm going to guess that these Blazer 45 colt loads spent at least two seasons in those cartridge loops.
Being in the construction industry for 40 years now, I know that the more noble metal (copper) should not remain in contact with a much lesser noble metal, such as aluminum. Galvanic corrosion will occur, and at an advanced pace with the presence of moisture.
But I never made the connection in ammo until I unloaded my cartridge belt to put it away one Spring. I was shocked at first when I saw these rounds in this condition. Until it dawned on me what had happened.
I no longer keep aluminum cased copper bullets for any length of time. I just shoot them soon after I find a sale I can't pass up. I've kept this one as a reminder/keepsake.