Are you sure its a tarnished lead? Lots of lightning cables have one tarnished lead (often on each side) from arcing. If I remember correctly using such a cable

Are you sure its a tarnished lead? Lots of lightning cables have one tarnished lead (often on each side) from arcing. If I remember correctly using such a cable in a new iPhone could even damage the matching pin inside the phone, leading to the situation where it would start arcing on a non-broken cable (damaging the same leads on the new cable).