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Resistance of grease to water contamination: Importance & Test Methods
In Summary
Resistance of grease to water contamination is critical because water contamination expedites rust and corrosion in mechanical components, drastically shortening their life and leading to pressure‑crack failures. To combat this, ASTM D4049 and ASTM D1264 outline tests that evaluate how well a grease adheres to a metal surface when subjected to a water spray and how much grease remains on a bearing after exposure to direct water.
Results from these water spray and water washout tests guide the selection of greases that will prolong the life of machinery. Instruments like the Koehler K18201 Digital Water Spray Apparatus and the K19201 Digital Water Washout Tester provide controlled conditions—constant temperature reservoirs, spray chambers and accurate temperature measurement—so technicians can evaluate grease performance and calculate the percentage of grease washed off.
What is the water spray test and why is it important in evaluating grease resistance to water contamination?
The water spray test is defined by ASTM D4049 and measures the ability of a grease to adhere to a metal surface when it is exposed to a controlled water spray. During the test a standardized metal plate coated with grease is subjected to a water stream at a specified rate and pressure for five minutes.
The percentage of grease washed off is calculated from weight measurements before and after spraying, which helps determine how well a particular grease will stay in place under wet conditions. This is important because the results inform the selection of greases that can maintain lubrication on machinery such as steel‑mill rock‑neck bearings, reducing the need for frequent replacement and repair.
How does the water spray apparatus measure grease adhesion in water contamination testing (ASTM D4049)?
Koehler’s K18201 Digital Water Spray Apparatus is designed to conform to ASTM D4049. It sprays water at the required rate and pressure while maintaining a constant temperature thanks to its integrated reservoir and spray chamber. The instrument uses a standardized grease‑application plate to help with sample preparation and testing.
Temperature stability is maintained within ±1 °F, and two thermometer wells independently measure the temperatures of the reservoir and water spray to ensure accurate conditions. After five minutes of spraying, technicians reweigh the plate to calculate the percentage of grease sprayed off, providing a quantitative measure of adhesion.
What is the water washout test for grease water contamination resistance (ASTM D1264)?
The water washout test follows ASTM D1264 and evaluates the resistance of grease to washout from a ball bearing under prescribed laboratory conditions. A packed bearing is weighed, exposed to a direct water spray for one hour and then reweighed.
By comparing the weight before and after the test, technicians determine the percentage of grease lost. This percentage indicates how well the grease can resist being washed out of bearings in service, which is critical for applications exposed to rain or spray.
What features does a water washout tester provide for grease water contamination testing (ASTM D1264)?
The K19201 Digital Water Washout Tester measures how much grease remains intact in a prepared bearing when it is exposed to a direct water spray. It features a water reservoir with a cartridge heater, a thermoregulator and a thermometer port that allow accurate control at temperatures of 100 °F and 175 °F (38 °C and 79 °C).
A two‑pulley system circulates water while it is heated, ensuring uniform temperature throughout the test. By using this instrument, technicians can run tests under realistic conditions and determine the percentage of grease lost from the bearing, which informs maintenance schedules and lubricant selection.
Why is grease resistance to water contamination critical for machinery performance and reliability?
Proper lubrication is essential for the longevity and sustainability of mechanical components. Water contamination can accelerate rust and corrosion in greases, leading to pressure cracks and a significant reduction in component lifespan. By analysing a grease’s behaviour when exposed to water, engineers can select products that protect bearings and other parts from premature failure.
Evaluating washout and spray‑off percentages helps ensure that lubrication remains in place during operation, thereby enhancing both the safety and the economic efficiency of machines.
How do you calculate grease water washout percentage and spray-off percentage in ASTM grease testing?
Both the water washout and water spray tests use weight measurements to determine how much grease remains after exposure.
For the water washout test, the percentage of grease lost (% washout) is calculated by subtracting the weight of the bearing after the test (W₃) from the weight of the packed bearing (W₂), dividing by the difference between the packed bearing and the clean bearing (W₂ − W₁), and multiplying by 100. A similar formula is used for the spray‑off test: the percentage of grease sprayed off is calculated by comparing the weights of the applicator plate before loading (W₁), after application (W₂) and after spraying (W₃), and applying the formula % spray‑off = (W₂ − W₃) / (W₂ − W₁) × 100. These formulas quantify how much lubricant remains, allowing objective comparison between greases.
'Water contamination testing of greases is essential for ensuring long-term performance, reliability, and protection of mechanical components in demanding environments.'
How do you perform a water spray test for grease water contamination according to ASTM D4049?
To run the water spray test with the K18201 Digital Water Spray Apparatus, technicians first switch on the instrument and fill it with water to the specified mark, allowing it to heat to the required temperature. A clean applicator plate is weighed, and a thin layer of grease—about 0.8 mm ± 0.005 mm thick—is spread onto the plate before reweighing.
The prepared panel is inserted into the spray apparatus, and the water spray is applied for five minutes (±15 seconds). After the test, any sample outside the edge of the plate is wiped off, and the plate is reweighed to calculate the percentage of spray‑off according to ASTM D4049. This procedure ensures consistent test conditions and accurate results.
How do you perform a water washout test for grease resistance to water contamination (ASTM D1264)?
The bearing is weighed before loading (W₁), after packing with grease (W₂) and after the washout test (W₃). The water reservoir’s cartridge heater and thermoregulator maintain the test temperature at either 100 °F or 175 °F, and the two‑pulley system circulates the water to ensure uniform heating. After the test, the percentage of grease lost is calculated using the formula described above, helping evaluate grease performance under washout conditions.
What to do Next?
To explore how water spray and water washout testing can support your grease evaluation and lubricant selection, view SciMed’s range of petroleum testing instrumentation designed for ASTM-compliant analysis.
Alternatively, if you would like guidance on selecting the right solution for your application or understanding how to implement these test methods in your workflow, speak to one of SciMed’s product specialists today.
Page FAQ's
It measures the ability of a grease to adhere to a metal surface when exposed to a water spray, providing a percentage of grease washed off within five minutes.
It evaluates how resistant a grease is to being washed out of ball bearings under water exposure, helping determine suitable applications for the lubricant.
By weighing the applicator plate before loading, after applying the grease and after the water spray, then using the formula (W₂ − W₃) / (W₂ − W₁) × 100.
By weighing the bearing assembly before loading, after packing with grease and after the washout test, then applying the formula (W₂ − W₃) / (W₂ − W₁) × 100.
The K19201 water washout tester maintains accurate temperatures of 100 °F (38 °C) and 175 °F (79 °C) using a cartridge heater, thermoregulator and circulating system
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