The ability of lubricating grease to withstand the addition of water to the lubricant system without adverse effects. Water Resistance is generally considered to be made up of four components as listed below:
Water Washout Resistance â€“ The ability of a lubricating grease to resist being removed from a bearing when operated with exposure to water. (Generally measured by ASTM D1264).
Water Absorption Characteristic â€“ The characteristics of a lubricating grease when water is added to the lubricating system. Water Absorption Characteristics may be measured by any of several suitable tests in which the lubricating grease may react in any of three ways, described as follows:
Water Soluble â€“ The lubricating grease absorbs the water, and then de-gels to semi-fluid consistency.
Water Absorbent â€“ The lubricating grease absorbs relatively large quantities of water with small or no change in consistency, and without leaving free water as a separate phase
Water Resistant â€“ The lubricating grease does not absorb more than small amounts of water, does not change appreciably in consistency, and leaves the added water as a second phase in the system.
Water Corrosion Resistance â€“ The ability of a lubricating grease to prevent corrosion of metal surfaces when water is present in the lubricating system. May be measured either statically by any of a number of standard tests, or dynamically by actual operation of bearings with water added to the lubricant reservoir (refer to ASTM D1743, D5969, and D6138).
Water Spray Resistance â€“ The ability of a grease to resist displacement from a surface by the impact of water spray. The method of test used to evaluate this characteristic for lubricating greases is given in ASTM D4049
Lubricating greases for various types of service may need any of the several types of water resistance characteristics described above, so that they are not measures of quality except for specific situations where particular properties are required.
Damage that involves the cumulative and gradual removal of material from surfaces. Three types of wear are described below:
Abrasive Wear â€“ Damage that occurs when surfaces are in contact and undergo relative motion, and cutting or abrasion by hard particles (usually a contaminant) remove material from the surfaces.
Adhesive Wear â€“ Damage that occurs when two surfaces are in contact and undergo relative motion, and high loads and/or temperatures cause asperities on these two surfaces to weld together and then immediately tear apart, removing material from one or both surfaces. Adhesive wear can be mild (frosting), moderate (scuffing), or severe (galling, scoring, seizing).
Corrosive Wear â€“ Damage that occurs when chemical reactions at a surface result in the removal of material. Corrosion can be localized (e.g., pitting) or general (not local).
The subjection of lubricating grease to any form of agitation or shearing action beyond simple transfer to any test apparatus.