ASTM D6547 Standard Test Method for Corrosiveness of Lubricating Fluid to Bimetallic Couple
5. Apparatus
5.1 Desiccating Jars, two.

5.2 Magnifier, 10x power.

5.3 Glass Stirring Rod.

5.4 Abrasive Papers, silicon-carbide or aluminum oxide (150, 240, 400, 600 grit, one sheet per disk).

5.5 Cloth, lint-free, clean, dry.

5.6 Chromium Alloy Steel Disks, three for each test sample.

5.7 Brass Clips, three for each test sample.

6. Reagents and Materials
6.1 Purity of Reagents - Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all reagents conform to the Committee on Analytical Reagents of the American Chemical Society where such specifications are available.

6.2 Etching Solution, consisting of distilled water, 450 mL; nitric acid, concentrated, 225 mL; sulfuric acid, concentrated, 300 mL; and hydrochloric acid, concentrated, 8 mL.
6.2.1 To avoid hazardous reactions when preparing the etching solution, place the distilled water (450 mL) in a 1.5 L, or larger, glass beaker set in a container of ice and water. Stir with a glass mechanical stirrer or plastic coated magnetic spin bar while slowly adding concentrated sulfuric acid (300 mL). Add more ice to the cooling bath as needed. When acid addition is complete, continue stirring until the solution has cooled to room temperature, and then start slow addition of the concentrated nitric acid (225 mL). Continue stirring after acid addition until the solution has cooled to room temperature, and then add concentrated hydrochloric acid (8 mL). Allow the mixture to equilibrate to room temperature before use. (Warning - Nitric, hydrochloric, and sulfuric acids are very corrosive. Nitric acid and sulfuric acid are also oxidizing acids. The analyst should prepare the etching solution in a well-ventilated hood and wear appropriate gloves, apron, and face shield.)

6.3 Acetone, technical grade. (Warning - Flammable. Health hazard.)

6.4 Distilled Water.

NOTE 2 - Both distilled and deionized water were used in the round robin with no apparent impact on test outcome.

6.5 Saturated Aqueous Solution , in contact with excess calcium nitrate tetrahydrate.

NOTE 3 - A saturated aqueous solution in contact with an excess of Ca(NO3)2·4H2O will produce 51 % relative humidity within a closed space at 25 °C. To prepare the saturated solution, dissolve 660 g of Ca(NO3)2·4H2O in 100 cc of water at 30 °C.

6.6 Low-Erucic Rapeseed Oil, commercial grade.

NOTE 4 - Low-erucic rapeseed oil may be used at the operator's discretion as a failing reference fluid to monitor test severity.

7. Test Specimen
7.1 Gather reagents and materials before beginning specimen preparation. The specimens must be prepared and assembled for testing on the same day to reduce formation of passivating oxide films on the surface of the bimetallic couple. For each test fluid, prepare three steel disks. These steel disks may either be new or from a previous test.
7.1.1 The steel disks shall consist of a chromium alloy steel in accordance with Specification A322 (E52100 or G52986), heat treated to Rockwell C-62. When new, the steel disks shall be 25.4 mm (1.00 in.) in diameter by 13 mm to 25 mm (0.5 in. to 1.0 in.) thick. Prior to initial use, the steel disk shall be ground on one side to a 0.51 µm (20 µin.) rms. This treatment need not be repeated prior to reuse.

7.1.2 Polish the surface of the ground side using 150, 240, 400, and 600-grit silicon carbide or aluminum oxide paper in succession. Use one sheet of each per disk. Perform each polishing operation at right angles to the previous one, and continue until all the cross scratches from the previous operation are removed.

NOTE 5 - Hand polishing techniques were used exclusively in the round robin evaluation of this test method. Mechanical polishing was not evaluated and may not yield equivalent results.

7.1.3 Clean the disks by wiping with a clean, dry, lint-free cloth, being careful not to touch the polished surfaces with bare hands.

7.1.4 Examine with a 10x power magnifier for discoloration, etching, pitting, or other signs of corrosion. Discard disks with any signs of corrosion.

7.1.5 Store the disks in a desiccator containing desiccant until time of use.

7.2 For each test fluid, prepare three brass clips. These brass clips may either be new or from a previous test.
7.2.1 The clips shall consist of a QQ-B-613, composition 2 brass, spring temper, fabricated to the dimensions shown in Fig. 1.

7.2.2 Place 150 mL of etching solution in a 250 mL beaker. Immerse the brass clips in etching solution for 20 s. Remove the clip from the etching solution and immediately wash successively in cold running water, distilled water, and acetone. If a visible stain remains on the clip in the area that will be in contact with the disk, repeat the etching process for an additional 20 s with fresh etching solution. Change etching solution and acetone every six clips. Allow the clip to air dry and store it in the desiccator until ready for use. Be careful not to touch the surface that will be in contact with the steel disks with bare hands.