Not all corrosion resistant bearings are completely waterproof. Corrosion resistant simply refers to an ability to operate when exposed to water, salt water, steam or other chemicals. Resistance varies depending on the material of the bearing. For example, 440 grade stainless steel bearings have good resistance to water and weak chemicals but will corrode in salt water or when submerged.
Alternatively, plastic bearings provide excellent corrosion resistance to water and salt water and can operate when submerged. There are a few alternative materials for rings, balls and cages, but the most appropriate depends on the exact application of the bearing.
316 Stainless steel bearings will operate fully submerged in potable water without corroding. They will even withstand submersion in seawater provided there is a regular flow of seawater over the bearing as the corrosion resistance of 316 steel depends on the presence of oxygen.
Ceramic bearings made from zirconia or silicon nitride can operate when fully submerged and are the best option for an ‘underwater bearing’. These bearings are completely unaffected by seawater and operate seamlessly when permanently underwater.
For more information on underwater bearings, contact the team on +44 (0) 1993 842 555 or sales@smbbearings.com.