Here’s a great example of some chafing wear that has deemed this engine frame useless. A nylon tie wrap was used to hold some cables in place directly against the engine frame. Over the course of time, the engine vibration caused this wear mark which was deep enough into the metal to easily feel with your finger. The nylon tie wrap was undamaged in this area, only the paint and steel frame where damaged.
People often underestimate the abrasive qualities of plastics. But remember that nylon is very abrasion resistant, which is another way of saying…its abrasive.