Corrosiveness to copper from petroleum products by Copper Strip test
11. Procedure
11.1 General - There are a variety of test conditions, which are broadly specific to given classes of product but, within certain classes, more than one set of test conditions of time or temperature, or both, may apply. In general, aviation gasoline shall be tested in a pressure vessel at 100°C and other high vapor pressure fuels, like natural gasoline, at 40°C. Other liquid products shall be tested in a test tube at 50°C, 100°C or even higher temperatures. The conditions of time and temperature given below are commonly used and are quoted in the ASTM specifications for these products where such specifications exist. They are, however, guides only. Other conditions can also be used when required by specifications or by agreement between parties. The test conditions of time and temperature shall be recorded as part of the result (see 13.1).
11.2 Pressure Vessel Procedure - For use with aviation gasoline and higher vapor pressure samples.
11.2.1 For Aviation Gasoline and Aviation Turbine Fuel - Place 30 mL of sample, completely clear and free of any suspended or entrained water (see 9.3) into a chemically clean and dry 25-mm by 150-mm test tube. Within 1 min after completing the final preparation (polishing), slide the copper strip into the sample tube. Place the sample tube into the pressure vessel (Fig. 1) and screw the lid on tightly. If more than one sample is to be analyzed at essentially the same time, it is permissible to prepare each pressure vessel in the batch before completely immersing each pressure vessel in the liquid bath at 100 more or less 1°C (212 more or less 2°F), provided the elapsed time between the first and last samples is kept to a minimum. After 2 h more or less 5 min in the bath, withdraw the pressure vessel and immerse for a few minutes in cool water (tap water). Open the pressure vessel, withdraw the test tube and examine the strip as described in 11.4.
11.2.2 For Natural Gasoline - Carry out the test exactly as described in 11.2.1 but at 40°C (104°F) and for 3 h more or less 5 min.
11.3 Test Tube Procedure - For use with most liquid products.
11.3.1 For Diesel Fuel, Fuel Oil, Automotive Gasoline - Place 30 mL of sample, completely clear and free of any suspended or entrained water (see 9.3), into a chemically clean, dry 25-mm by 150-mm test tube and, within 1 min after completing the final preparation (polishing), slide the copper strip into the sample tube. If more than one sample is to be analyzed at essentially the same time, it is permissible to prepare each sample in the batch by stoppering each tube with a vented stopper, such as a vented cork before placing each tube in a bath maintained at 50 more or less 1°C (122 more or less 2°F), provided the elapsed time between the first and last sample prepared is kept to a minimum. Protect the contents of the test tube from strong light during the test. After 3 h more or less 5 min in the bath, examine the strip as described in 10.4. For tests on fuel oil and diesel fuel, to specifications other than Specifications D396 and D975, a temperature of 100°C (212°F) for 3 h is often used as an alternative set of conditions. Some automotive gasolines with vapor pressure above 80 kPa at 37.8°C have exhibited evaporation losses in excess of 10 % of their volume. If such evaporation losses are apparent, it is recommended that the Pressure Vessel Procedure (see 11.2) be used.
11.3.2 For Cleaners (Stoddard) Solvent and Kerosine - Carry out the test exactly as described in 11.3.1 but at 100 more or less 1°C (212 more or less 2°F).
11.3.3 For Lubricating Oil - Carry out the test exactly as described in 11.3.1, but the tests can be carried out for varying times and at elevated temperatures other than 100°C (212°F). For the sake of uniformity, it is suggested that even increments of 5°C, beginning with 150°C, be used.
11.4 Strip Examination
11.4.1 Empty the contents of the test tube into a suitably sized receiver. If a receiver made out of glass is used, such as a 150-mL tall-form beaker, let the strip slide in gently so as to avoid breaking the glass. Immediately withdraw the strip with forceps and immerse in wash solvent. Withdraw the strip at once, dry and inspect for evidence of tarnishing or corrosion by comparison with the Copper Strip Corrosion Standards. The step of drying the strip may be done by blotting with filter paper, air drying, or by other suitable means. Hold both the test strip and the standard strip plaque in such a manner that light reflected from them at an angle of approximately 45° will be observed.
11.4.2 In handling the test strip during the inspection and comparison, the danger of marking or staining can be avoided if it is inserted in a flat glass tube (see Appendix X1), which can be stoppered with absorbent cotton.
