Protection against corrosion
Grease should also protect the bearing against corrosion and should not be washed out of the bearing arrangement if water is present. The type of thickener solely determines the ability of the grease to resist water washout. Thickeners with very good washout resistance include lithium complex, calcium complex, and polyurea greases. The ability of a grease to inhibit corrosion is determined by the properties of the rust inhibitor additive for that grease.
For very low-speed applications, filling the housing up to 90% with grease can improve corrosion protection and help prevent the ingress of water.