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 – The ability of a lubricating grease to resist being removed from a bearing when operated with exposure to water. Generally measured by ASTM D1264 or ISO 11009.
Water Absorption – 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 – The lubricating grease absorbs the water, and then de-gels to semi-fluid consistency.
Water Absorbent – The lubricating grease absorbs relatively large quantities of water with little or no change in consistency and without a separate phase of free water.
Water Resistant – The lubricating grease does not absorb more than small amounts of water, does not change appreciably in consistency, and most of the added water is a separate second phase.
Water Corrosion Resistance – The ability of a lubricating grease to prevent corrosion of metal surfaces in the presence of water. 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, as in ASTM D1743, D5969, D6138 and ISO 11007.
Water Spray Resistance – 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 not need any of the several types of water resistance characteristics described above. They are not measures of quality except for specific situations where water resistance is required.