Bearings with special anti-corrosion coatings are available, but most bearings are not manufactured from corrosion resistant materials. When handling and storing bearings, care must be taken to ensure that they will not rust or corrode. Even a small amount of moisture or chemical left on an unprotected bearing by a glove or hand can result in a small etched area, which may initiate bearing fatigue. Most quality new and remanufactured bearings are shipped with a protective coating, are typically covered in a protective paper or other wrapping, and are shipped in a carton or crate. When receiving a new or remanufactured bearing, do not remove it from its packaging until ready to install in the application. Do not store bearings directly on concrete floors, where water can condense and collect on the bearing. Store the bearings on a pallet or shelf, in an area where the bearings will not be subjected to high humidity or sudden and severe temperature changes that may result in condensation forming. Always put oiled paper or, if not available, plastic sheets between rollers and cup races of tapered roller bearings.
Article taken from Timken Industrial Bearing Maintenance Manual