White plastic around lightning connector has fallen off and there is some kind of black corrosion on 4 of the pins. Is this normal?

My lightning cable has some black corrosion on the "gold" connectors and sometimes i have to turn it around for it to start charging. It appears it does not have good contact with the pins on the inside of my phone. Also the plastic around the connector did just slide of it and down the cable.. Is this normal with apple products??