CORROSION PREVENTIVE PROPERTIES CORROSIVENESS AND OXIDATION STABILITY OF OILS: ASTM D4636
EXPLANATION
This test method is a combination of Federal Test Methods 5307.2 and 5308.7. It is used to test hydraulic oils, aircraft turbine engine lubricants, and other highly refined oils to determine their resistance to oxidation and corrosion degradation and their tendency to corrode various metals. Petroleum and synthetic fluids may be tested using moist or dry air with or without metal test specimens.
Interpretation of results should be done by comparison with data from oils of known field performance. This test is most suitable for oils containing oxidation and corrosion inhibitors. Without such ingredient(s) the severe test conditions will yield rather drastic changes to the oil.
TEST SUMMARY
This test method consists of one standard and two alternative procedures. A particular specification needs to establish which of these tests should be used. A large glass tube containing an oil sample and metal specimens is placed in a constant temperature bath (usually from 100 to 360° C) and heated for the specific number of hours while air is passed through the oil to provide agitation and a source of oxygen. Corrosiveness of the oil is determined by the loss in metal mass, and microscopic examination of the sample metal surface(s). Oil samples are withdrawn from the test oil and checked for changes in viscosity and acid number as a result of the oxidation reactions. At the end of the test the amount of the sludge present in the oil remaining in the same tube is determined by centrifugation. Also, the quantity of oil lost during the test is determined gravimetrically.
Metals used in the basic test and alternative test Procedure 1 are titanium, magnesium, steel (two types), bronze, silver, and aluminum. Metals used in alternative test Procedure 2 are copper, steel, aluminum, magnesium, and cadmium.
Other metals may be specified.
TEST PRECISION
The precision and bias of this test method is being balloted in the DO2 Committee.
