Weathered dissuse

You will neglect upon the armor of your foes against the ravishes of time. Each turn the effect degrades the armor, from which the target must make a saving throw. Each fail reduces their ac from the armor by 1. This can stack, to a max of -3 ac. Items that offer a bonus ac of 3 or lower, will break next time they are hit in combat. This spell cannot be degrade below -3, and armor that withstands the weathering can be repaired with proper tools and materials. 

This spell does not effect enchanted items.