The marine industry offers a great challenge for bearing manufacturers due to the ever present risk of corrosion. Stainless steel bearings are commonly used in marine environments but 440 grade stainless steel has a limited resistance to seawater or salt spray. 440 grade stainless steel ball bearings can be passivated (see an explanation on passivation here) to increase corrosion resistance but they will eventually corrode in a marine environment unless protected from the elements.
Ceramic bearings made from zirconia or silicon nitride offer excellent corrosion resistance in a marine environment. Ceramic bearings are not affected by seawater so they can be used in marine environments where they are permanently submerged.
We also stock ball bearings manufactured from 316 grade stainless steel which is also known as marine grade stainless steel due to its ability to be used in marine applications above the water line or in flowing water. As this steel cannot be thermally hardened, 316 grade stainless steel bearings have much lower load and speed ratings.
Acetal resin bearings with 316 stainless steel or glass balls have very good resistance
to seawater but again, can only be used in lower precision low load and low speed
applications. The capacity of plastic bearings can be increased by using an alternative
material such as PEEK but these are still classified as semi-