The Basics:

When Water Meets Grease

By Lubrication SME Stacy Heston

The product data sheet provides a significant amount of information with regards to how a grease will perform. When it comes to the performance of a grease, there are two standards established by ASTM for testing a grease’s resistance to water. It is important to understand the results of these tests and how they are derived in order to make an informed decision about which grease is best for your application.

Resistance to Water Spray

ASTM D4049 is the standard for determining the resistance of a lubricating grease to water spray. This method looks at the grease’s ability to adhere to a metal surface when subject to spray. These results are useful for components such as chain drives, slides, etc. that are directly exposed to wash down spray.

To perform the test, a test panel is prepped and a layer of grease approximately 0.8 mm thick is applied. The test panel is then exposed to 276 kPa (40 psi) of water spray for approximately 5 minutes. The amount of grease removed is recorded as a percentage.

Resistance to Water Washout

ASTM D1264 is the standard method for determining the water washout properties for lubricating greases. The method basically looks at the amount of grease that is washed out of a bearing while in operation. A bearing is packed with 4 grams of test grease and the bearing is operated at 600 rpm. While in operation, water is circulated through at a rate of 5 mL/s for approximately 60 minutes.

This method is not considered to be the equivalent to a service evaluation test, but provides an environment representative of a grease lubricated bearing.

Grease Selection

Grease #1

Claim

Water resistant, won’t washout or emulsify

Available Test Data

Resistance to Water Spray, ASTM D4049; 5.0% Loss Typical

Grease #2

Claim

Highly resistant to water washout, water jet spray, and most sterilizing chemicals used in cleaning

Prevents bearing, gear, and equipment damage in moist or wet operations

Available Test Data

Water Washout Characteristics, ASTM D1264; 1.75% @ 79°C (174°F)

Resistance to Water Spray, ASTM D4049; 25.5% Loss

Grease #1 claims resistance to water and will not wash out. However, water washout results per ASTM D1264 are not readily available. Grease #2 claims to be resistant to water washout and water jet spray, but it has greater loss at 25.5% for water spray resistance. The washout resistance is 1.75%. Without the water washout results for Grease #1 readily available, one might conclude that Grease #1 would be the better grease for applications where the lubricant is exposed to water spray. For applications where the grease is exposed to water in an enclosed setting, such as a rolling element bearing, Grease #2 would be the better selection.