Most bare metal will corrode if exposed to moisture and other environmental factors. That’s a given. Traditional paints for metal are designed for corrosion prevention to preserve the appearance and integrity of the surface. These paints adhere strongly to the metal, and this adhesion is vital to the corrosion protection they provide. Typical paints are designed to be difficult to remove, and to last.
But bare metal parts that are temporarily stored or transported during processing often require a coating that will protect against corrosion and be easily removed just prior to final assembly. Considering strict specifications of many OEMs and suppliers, corrosion is not an option.