ASTM D6557 Standard Test Method for Evaluation of Rust Preventive Characteristics of Automotive Engine Oils
11. Test Results
11.1 Prepare Specimens for Image Analysis:
11.1.1 Remove the specimens from the test tubes, using forceps that are 180 mm long, with serrated tips).
11.1.2 Place each specimen into a separate scintillation wash vial (make one perforation in the bottom to facilitate cleaning), with a capacity of 20 mL, and then into a vial holder.
11.1.3 Put the vial holder into a utility tray (stainless steel, 310 mm by 200 mm by 60 mm), pour enough heptane into the tray to cover the specimens, and shake the tray gently for (30 to 60) s before decanting the heptane.
11.1.4 Put enough heptane (see 7.1.3) into the tray to cover the specimens, and soak the specimens for 10 min to remove any remaining organic deposits, before decanting the solvent.
11.1.5 Put enough heptane into the tray to cover the specimens, and shake the tray gently for (30 to 60) s before decanting the heptane.
11.1.6 Transfer the specimens into clean, dry scintillation vials of 20 mL capacity that have been previously labeled the same as the test tubes in 8.2.3.1.
11.1.7 Dry the specimens with nitrogen gas, and then securely fasten the vial caps.
11.2 Prepare Image Analysis System for Rust Evaluation:
11.2.1 Set the microscope adjustments as follows:
11.2.1.1 Illumination change-over knob B/D - D (dark field).
11.2.1.2 ND16 filter slider - IN (push to first click).
11.2.1.3 A filter slider - IN (push to second click).
11.2.1.4 F (field diaphragm control lever) - OPEN.
11.2.1.5 A (aperture diaphragm control lever) - OPEN.
11.2.1.6 Neutral density filter - ND16.
11.2.1.7 Objective lens - 5x.
11.3 Optronics Controller:
11.3.1 Shutter speed - 1/60 + (manual).
11.3.2 White balance - ON.
11.4 Turn on the Image Analysis Computer and initiate the Optimate software program.
11.5 Select the macro titled BRT51.MAC (BRT Macro Version 5.1, or later).
11.6 Rust Rating Procedure:
11.6.1 Wipe each specimen, using a lint-free laboratory wipe; remove all solvent film and loose surface deposits from the rating surfaces prior to the digital image rating.
11.6.2 Place the Calibration Reference Specimen onto the microscope stage, and follow the dialog box instructions that appear on the screen (operator interface) (see Fig. 8).
NOTE 7 - Refer to the software manual for the detailed procedure of imaging analysis.
11.6.2.1 Answer the operator interface questions to allow automatic recording of the data into the spreadsheet program.
11.6.3 Rotate (without skin contact) the Calibration Reference Specimen, and take 20 different readings.
11.6.3.1 The average gray value for the Calibration Reference Specimen at the start of the image analysis shall be 135 +/- 2. The average gray values for the Calibration Reference Specimen at the start and end of the image analysis shall not differ by more than 3.
11.6.4 Repeat the previous step for each specimen. (The Calibration Reference Specimen is the first and last specimen analyzed to ensure no drift has occurred during analysis.)
12. Precision and Bias
12.1 Precision:
12.1.1 Intermediate Precision (formerly called repeatability) - The difference between two results obtained with the same oil, using the same test method, in the same laboratory, using the same apparatus (different test tubes), would, in the normal and the correct operation of the test method, exceed the following value in only one case in twenty:
15.15 AGV
12.1.2 Reproducibility - The difference between two single and independent test results obtained with the same oil in different laboratories would, in the normal and the correct operation of the test method, exceed the following value in only one case in twenty:
18.89 AGV
12.2 Bias - No bias is believed to exist. However, this aspect of the test will be reevaluated after the test method has been in use by several laboratories over an appropriate period of time.
13. Keywords
13.1 Ball Rust Test; corrosion; engine oil; rust
