ASTM D2619 Test Method for Hydrolytic Stability of Hydraulic Fluids (Beverage Bottle Method)
7. Procedure
7.1 Fill the pressure beverage bottle with distilled water and allow to stand overnight. Drain and rinse, with distilled water, but do not dry.
7.2 Weigh 75 g of test fluid and 25 g of distilled water to 0.5 g into the beverage bottle.
7.3 Polish the copper test specimen to a clean surface with the steel wool and wash with n-heptane. (Warning - see Note 3). Dry and weigh to 0.2 mg. Immediately immerse the copper specimen in the test fluids in the beverage bottle. Avoid specimen contact by handling the cleaned copper test strip with cotton gloves or filter paper.
7.4 Prepare a disk of the inert seal and place in a new bottle cap. Seal the bottle using the cap with the gasket.
7.5 Place the bottle in the rotating mechanism in the oven adjusted to 93 +/- 0.5°C (200 +/- 1°F). Allow to rotate, end for end, at 5 rpm for 48 h.
7.6 Remove the bottle and place on an insulated surface until cool.
7.7 Open the bottle, empty the contents into a 100-mL, cone-shaped centrifuge tube, and centrifuge for 10 min at 1500 rpm. Decant the separated water and emulsion layers and set aside. (A pipet can be used as an alternative method to remove the water layer without centrifuging, provided a clear water separation results by sample settling.)
7.8 Filter the fluid oil layer through a membrane filter weighed to 0.2 mg. Transfer the fluid layer to a 125-mL separatory funnel. Rinse the filter flask with 25 mL of distilled water and add to the separatory funnel. Repeat the water washes of the oil in the separatory funnel until the washings are neutral to litmus. Save the combined water washings (Note 6). Dry the filtered, washed fluid by vacuum dehydration when in contact with anhydrous sodium sulfate (Note 7). Filter the fluid through filter paper to remove the sodium sulfate solids.
NOTE 6 - If the fluid sample is heavier than water, drain the fluid from the separatory funnel, remove the water wash, and return the fluid to the separatory funnel for repeated water washes.
NOTE 7 - Mechanical stirring for 1 h with the anhydrous sodium sulfate dries the fluid efficiently. This is done prior to vacuum dehydration.
7.9 Determine the viscosity of the filtered fluid in accordance with Test Method D445. Compare the result with viscosity of the original fluid sample and calculate the percentage viscosity change at 40°C (104°F).
7.10 Determine the total acid number of the filtered fluid in accordance with Test Method D974. Acidity for the filtered fluid is compared to that of the original fluid and the acid number change recorded.
7.11 Filter the water phase and the emulsion layer (which usually contains the bulk of the insoluble material) through the membrane filter. Rinse the copper test specimen, pipet, centrifuge tube, beaker, and beverage bottle with distilled water and n-heptane. Filter these washes through the membrane. Segregate the water wash. Then wash with 50 mL of n-heptane. Dry the membrane in a 60°C (140°F) oven and weigh. Calculate the percentage of insolubles in the 75-g sample.
7.12 Combine all the water portion and washes. Determine total acidity by adding 1.0 mL of phenolphthalein solution and titrating rapidly with 0.1 N KOH solution to the appearance of pink phenolphthalein end point which persists for 15 s. Calculate the water layer acidity as follows:
Total Acidity, mg KOH = [(A - B)N] x 56.1
where:
A = millilitres of KOH solution required for titration of the sample,
B = millilitres of KOH solution required for titration of the blank, and
N = normality of KOH solution.
7.13 Wash the copper specimen with warm n-heptane, followed by warm 1,1,1-trichloroethane. (Warning - See Note 5.) Brush with a short bristled typewriter-type brush while washing in both solvents. Dry and weigh and examine under a 20x microscope. Report appearance and weight loss in milligrams per square centimetre.
