NB/SH/T 0723-2014 Corrosiveness evaluation method for diesel engine oils under 121℃

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Card type: Test method

1. Method number / full title / English name / replacement relationship

• Standard number: NB/SH/T 0723—2014
• Chinese full title: Corrosiveness evaluation method for diesel engine oils under 121℃
• English name: Standard test method for evaluation of corrosiveness of diesel engine oil at 121℃
• Replacement relationship: replaces SH/T 0723—2002 "Corrosiveness evaluation method for diesel engine oils"
• Adoption relationship: modified adoption by redrafting method of ASTM D5968-06 "Corrosiveness evaluation method for diesel engine oils under 121℃"
• Publication/implementation: published on 2014-06-29, implemented on 2014-11-01
• Issuing authority: National Energy Administration
• Previous versions: SH/T 0723—2002
• Main technical changes compared with SH/T 0723—2002 (as listed in the source text):
  • The standard title was changed to "Corrosiveness evaluation method for diesel engine oils under 121℃"
  • Deleted content related to "air source, -68° dew point"
  • Deleted content related to "sandpaper cannot be dry, wet or waterproof sandpaper"
  • The immersion depth of the heating tube was changed from "30 cm±5 cm" to "23 cm~35 cm"
  • The calibration of instruments used in this test method and the determination of the validity of test results require testing and judgment using the reference oil provided by TMC (see 9.1)
  • The expression and provisions of the precision of the standard method were modified
• Main differences from ASTM D5968-06 (as listed in the source text): some referenced standards adopt the corresponding national standards of our country; only the report formats of Annex A.1 and A.2 in ASTM D5968-06 are adopted, and the data dictionary in A.2 is not adopted

2. Scope of application and non-applicability

• This standard specifies a test method for characterizing the corrosiveness of a sample by measuring the metal content in the oil before and after oxidation.
• It is applicable to detecting the corrosion tendency of diesel engine oils toward metals such as copper and lead contained in cam followers and bearings in diesel engines.
• Not applicable: not provided in the available source.

3. Method principle

Four metal test specimens of copper, lead, tin and phosphor bronze are immersed in a certain amount of diesel engine oil sample, a fixed amount of air is passed into the sample at high temperature, and after the test is completed, the metal test specimens and the sample are respectively subjected to corrosiveness testing. In each group of tests, a reference oil test is also carried out to verify whether that test is valid. (Chapter 3)

Method application (Chapter 4): This test method is mainly used to simulate the corrosion process of non-ferrous metals in diesel engine oils. The corrosion process studied is mainly caused by certain chemical substances in the lubricating oil rather than by degradation or contamination of the lubricating oil. A large amount of road test data proves that this test method is correlated with cam and bearing failures caused by corrosion.

4. Reagents and materials (purity / preparation)

4.1 Reagents

• 6.1.1 Reagent purity: unless otherwise specified, analytical grade reagents may be used in all tests.
• 6.1.2 Acetone: sulfur-free. (Warning: flammable, harmful)
• 6.1.3 Degreasing solvent: trichlorotrifluoroethane or 1,1,1- trichloroethane. (Warning: harmful if inhaled)
• 6.1.4 Glassware cleaning solution: chromic acid cleaning solution, prepared by mixing 35 mL saturated sodium dichromate (hydrated) and 1000 mL sulfuric acid. (Warning: can cause burns)
• 6.1.5 Glassware carbon remover (optional): Oakite detergent R-8. (Warning: can cause burns)
• 6.1.6 Tetrahydrofuran. (Warning: flammable, toxic and harmful)
• 6.1.7 Solvent naphtha: aromatic-containing naphtha or solvent naphtha No. 2 conforming to GB 1922—2006. (Warning: flammable, toxic and harmful)

4.2 Materials

• 6.2.1 Metal test specimens: dimensions are 2.5 cm×2.5 cm×0.081 cm, each metal test specimen has two holes, see Figure 7. The material and types are copper (R401-A), lead (R401-Lead), tin (R401-tin), phosphor bronze (R401-LEADz). Note: Metal test specimens can be purchased from Test Engineering INC. in the United States.
• 6.2.2 Metal wire: nickel-chromium alloy material, clean, used to connect metal test specimens.
• 6.2.3 Sandpaper: 58.5 μm (240 grit) aluminum oxide and 35.0 μm (400 grit) silicon carbide sandpaper. Do not use sandpaper containing iron-based abrasives, such as natural emery.
• 6.2.4 Absorbent cotton: with good hygroscopicity.
• 6.2.5 Filter paper, silk cloth.
• 6.2.6 Reference oil: provided by TMC of ASTM.
• 6.2.7 Detergent: for cleaning glassware.

5. Apparatus and equipment

5.1 Standard-wall-thickness borosilicate glass apparatus

• 5.1.1 Sample tube: see Figure 1.
• 5.1.2 Sample tube elbow: see Figure 2.
• 5.1.3 Air tube: see Figure 3.
• 5.1.4 Thermocouple tube: see Figure 4.
• 5.1.5 Condenser tube: see Figure 5.
• 5.1.6 Assembled apparatus: see Figure 6.

5.2 Other glass apparatus and accessories

• 5.2.1 Spacer: used to separate metal test specimens, made of standard-wall-thickness borosilicate glass, outer diameter 9 mm, length 6 mm.
• 5.2.2 Sampling tube: made of borosilicate glass, outer diameter 4 mm, length about 600 mm, U type, the outlet end is connected to a 25 mL suction filter flask, and its length should be suitable.
• 5.2.3 Connector: made of polytetrafluoroethylene, 10/18 connector, used to seal the air tube and the sample tube elbow.

5.3 Other apparatus

• 5.3.1 Heating bath: temperature control accuracy is ±0.5℃, immersion depth 23 cm~35 cm, either an oil bath or an aluminum block bath may be used. (Warning: the instrument surface temperature is high, protective measures should be taken to avoid direct skin contact)
• 5.3.2 Fume hood: to remove flue gas generated during heating.
• 5.3.3 Air source: use a clean, dry air source.
• 5.3.4 Flowmeter: flow range 10 L/h±1 L/h.
• 5.3.5 Analytical balance: sensitivity 0.1 mg.
• 5.3.6 Balance: range 2500 g, sensitivity 0.1 g.
• 5.3.7 Microscope: magnification 20.
• 5.3.8 Fixture: square wooden fixture with grooves, used to fix metal test specimens; the metal test specimens are tied with metal wire, see Figure 7.
• 5.3.9 An air dryer may optionally be used to meet the requirements of 5.3.3. Use a glass tube filled with anhydrous calcium sulfate as the dryer, and control the linear velocity of air passing through the tube to not exceed 1.2 m/min.
• 5.3.10 Drying oven (optional): for drying glassware at high temperature.
• 5.3.11 Tweezers: made of stainless steel.
• 5.3.12 Thermocouple.
• 5.3.13 Brush: short stiff bristles.

6. Recommended operating conditions

• Sample temperature: 121℃±0.5℃ (8.1.3)
• Heating bath immersion depth: 23 cm~35 cm (5.3.1, 8.1.3)
• Air flow rate: 5 L/h±0.5 L/h (8.2)
• Test time: 168 h (8.2)
• Distance from the outlet end of the air tube to the bottom of the sample tube: not more than 0.3 cm (8.1.5)
• Sample amount: 100 mL±1 mL (8.1.2)
• Air dryer linear velocity (optional): not more than 1.2 m/min (5.3.9)

7. Sampling and sample preparation

• 8.1.1 Place the bundle of metal test specimens vertically into the sample tube (so that the air tube contacts the bottom of the sample tube), and weigh the total mass of the air tube, sample tube and their contents to the nearest 0.1 g.
• 8.1.2 Add 100 mL±1 mL of sample to the sample tube, weigh again the total mass of the air tube, sample tube and their contents to the nearest 0.1 g, and calculate the sample mass.
• 8.1.3 Place the sample tube into the heating bath with an immersion depth of 23 cm~35 cm, connect the sample tube to the condenser tube and other components as shown in Figure 6, and control the sample temperature at 121℃±0.5℃.
• 8.1.4 Pass cooling water through the condenser tube.
• 8.1.5 Pass the air tube (outlet end downward) through the condensation section and into the sample, and adjust its outlet end so that the distance from the bottom of the sample tube is not more than 0.3 cm.

Preparation of metal test specimens (7.4)

• 7.4.1 Clean the metal wire with tetrahydrofuran and acetone, and air dry. (Warning: this operation and the following preparation process should be carried out in a fume hood)
• 7.4.2.1 First use 58.5 μm (240 grit) sandpaper to grind away dirt from both surfaces and the four edges of the square metal test specimen, including the inner edge of the small holes, then use 35.0 μm (400 grit) sandpaper wetted with acetone for fine grinding to remove previous grinding marks. Preferably, place the 35.0 μm (400 grit) sandpaper flat, and rub the metal test specimen longitudinally on the 35.0 μm (400 grit) sandpaper in a direction perpendicular to the grinding direction of the 58.5 μm (240 grit) sandpaper. Each sheet of sandpaper may only be used for wiping the same type of metal test specimen.
• 7.4.2.2 In all subsequent steps, the metal test specimens must be handled with tweezers or filter paper. If there are a large number of defects or particles on the metal test specimen, they should first be ground away with coarse sandpaper, then ground with 58.5 μm (240 grit) sandpaper and 35.0 μm (400 grit) sandpaper.
  • a) Place the ground metal test specimen in tetrahydrofuran.
  • b) After all metal test specimens have been ground, remove the metal test specimens from the tetrahydrofuran and wipe them with clean absorbent cotton until the used absorbent cotton remains as clean as new.
  • c) Then rinse the metal test specimens with tetrahydrofuran and place them in a desiccator to dry.
  • d) Weigh the metal test specimens as soon as possible to the nearest 0.1 mg.
  • e) Fix the metal test specimens with the fixture in the order of lead, copper, tin, phosphor bronze, see Figure 7.
• 7.4.2.3 Use tweezers to pick up the clean metal wire, tie the metal test piece securely, see Figure 7.

Cleaning of glassware (7.1, 7.2)

• 7.1.1 Clean all glassware and accessories with a degreasing solvent to remove residual oil, and air-dry.
• 7.1.2 Immerse all glassware and accessories in glassware decarbonizing agent to remove deposits, then rinse with water.
• 7.1.3 Clean the glassware and accessories with detergent, then rinse off the detergent with water, and dry.
• 7.1.4 Place the above apparatus in a dust-proof cabinet and take it out when testing. If stored for more than one week, it should be cleaned with distilled water, dried, and then used.
• 7.1.5 If there are special requirements or in arbitration testing, all glassware should be further carefully cleaned. Soak all glassware in glassware cleaning solution 3 h~16 h.
• 7.1.6 Take out the glassware, first rinse several times with tap water, then rinse with distilled water, and dry.
• 7.2 Cleaning of unused glassware: follow the steps of 7.1.3 and 7.1.6, omitting steps 7.1.1, 7.1.2, 7.1.4 and 7.1.5.
• 7.3 Apparatus assembly: Assemble the apparatus as shown in Figure 6, and lubricate the joints with the sample.

8. Analysis procedure

• 8.2 Test process: Connect the air tube to an air source that provides clean dry air. At the start of the test, introduce air into the sample at a flow rate of 5 L/h±0.5 L/h, and maintain for 168 h.
• 8.3 Inspection and disassembly of the apparatus at the end of the test:
  • 8.3.1 Disconnect the air source and remove the condenser tube.
  • 8.3.2 Remove the sample tube from the heating bath, and after cooling, wipe the exterior clean with a cloth moistened with solvent oil.
  • 8.3.3 Weigh again the total mass of the air tube, sample tube and their contents, to the nearest 0.1 g, calculate the remaining sample mass, and determine the percentage evaporation loss of the sample mass. If the percentage evaporation loss is greater than 8%, it indicates leakage; eliminate the source of leakage, and repeat the test with a new sample and a new metal test piece.
  • 8.3.4 Use tweezers to take the metal test piece out of the sample tube, remove the metal wire, and retain the sample tube and sample for further testing.
• 8.4 Treatment of metal test pieces:
  • 8.4.1 Use tweezers to hold the test piece and clean it separately in tetrahydrofuran.
  • 8.4.2 Repeat cleaning the metal test piece with fresh tetrahydrofuran, then scrub with a brush until the tetrahydrofuran no longer changes color. Use a silk cloth moistened with acetone to wipe the metal test piece repeatedly until the silk cloth remains clean, then air-dry. Phosphor bronze test pieces may be more difficult to clean because of strong adhesion of reaction products; improper removal of reaction products from the metal test piece can affect the measurement result of the metal test piece mass change. When scrubbing phosphor bronze test pieces, more force should be used to remove the surface reaction products, but care should be taken not to rub the already clean and smooth parts of the test piece.
• 8.5 Test piece inspection:
  • 8.5.1 Weigh each metal test piece separately, to the nearest 0.1 mg, and calculate the mass change per unit area of the metal test piece, in units of mg/cm².
  • 8.5.2 Use method GB/T 5096 to rate the corrosion on both sides of the copper piece, and record the stain colors appearing on the copper piece and phosphor bronze piece.
• 8.6 Testing of new samples and tested samples: As soon as possible, use method GB/T 17476 to analyze the concentrations of copper, lead and tin in the new and tested samples, with duplicate determinations for each sample.

Reference oil test (Chapter 9)

• 9.1.1 When using this standard for testing, a reference oil test shall be conducted in each group of tests to verify whether that test is valid.
• 9.1.2 The reference oil test conditions are exactly the same as the sample test conditions.
• 9.1.3 The reference oil for this standard is provided by TMC of ASTM. The range of test results for this reference oil is known. Only when the reference oil test results meet the acceptance criteria provided by TMC are the test results of the same batch of samples valid.
• 9.2 Reference oil test organized by TMC:
  • 9.2.1 Before conducting the reference oil test, purchase reference oil directly from TMC. These oils have specific chemical compositions, and each reference oil package has a number for identification. Provide numbered reference oils for blind sample testing so that possible deviations in test results can be summarized and analyzed.
  • 9.2.2 While testing each group of samples, conduct a reference oil test with a TMC code, under test conditions exactly the same as the sample determination. Laboratories participating in the organization of TMC must, according to TMC of ASTM, issue the "ASTM Principles for the Application and Analysis of Reference Oils", use the designated reference oil for testing, and conduct the reference oil test and report the test results according to the guidelines of TMC.
  • 9.2.3 Before testing, apply to TMC. TMC will designate a certain reference oil for testing and inform the laboratory of the reference oil number.
  • 9.2.4 Conduct the reference oil test according to the same test procedure as for the sample.
  • 9.2.5 Report the reference oil test results according to the following requirements:
    • 9.2.5.1 Report the reference oil test data to TMC using the report format in Appendix B, reporting only reference oil-related data, not including sample test data.
    • 9.2.5.2 The test results may be reported to TMC by fax or electronic transmission.
    • 9.2.5.3 In addition to transmitting the test results to TMC by fax or electronic transmission, a formal test report with a handwritten signature must also be mailed. The signature on the report cover (see Table B.1) shall be the original signature of the laboratory manager and shall not be photocopied, to confirm the authenticity of the test process. Ensure that TMC receives the mailed formal test report within 30 days after the test completion date.
  • 9.2.6 Evaluation of reference oil test results: After TMC receives the reference oil test results, it will check the operation process according to the procedure. If the test operation process is valid, the reference oil test results will be evaluated using the acceptance criteria determined by the supervisory body. The reference oil acceptance criteria may be modified by the supervisory body.
    • 9.2.6.1 If the reference oil test is proven to have valid operation and the test results meet the acceptance criteria, the laboratory will receive acceptance information. At the same time, the blind sample results will be notified to the laboratory. TMC will only finally determine the validity of the test after receiving and checking the formal report with a handwritten signature. Inconsistency between the initially transmitted data and the final formal report data will lead to suspension and rejection of the decision on test validity.
    • 9.2.6.2 If the TMC reference oil test is proven invalid, TMC will provide the laboratory with an explanation of the problems related to the test failure. If the cause of the test failure is clear, the laboratory should correct it before applying for the next group of reference oil tests. If the cause of the test failure is unclear, the laboratory should re-inspect the test-related equipment according to operating rules and laboratory specifications, and then apply for the next group of reference oil tests.
  • 9.2.7 Correlation between reference oil test and sample test: Only when the reference oil test results meet the acceptance criteria provided by TMC can the same batch of sample tests be considered valid.

9. Qualitative and quantitative and calculation formulas

10.1 Percentage evaporation loss L (%)

L = (W₁ − W₂) / Wₐ × 100 …… (1)

• W₁: Total mass of air tube, sample tube and contents (including sample) before test, g
• W₂: Total mass of air tube, sample tube and contents (including sample) after test, g
• Wₐ: Initial mass of sample, g
• Note: The formula symbols are unclear in the source transcription; verify the symbols and their meanings against the original before calculation.

10.2 Mass change of metal test piece M (mg/cm²)

M = (M₁ − M₂) / [2 × (W × L₀)] …… (2)

• M₁: Mass of metal test piece after test, mg
• M₂: Mass of metal test piece before test, mg
• W: Width of metal test piece, cm
• L₀: Length of metal test piece, cm
• Note: The symbols in the original formula are doubtful due to the presence of source-text extraction ("M-M," "WXL." etc.), requires confirmation against the source standard (source-text extraction).

10.3 Change in metal concentration in sample and reference oil after test C (mg/kg)

C = C₂ − C₁ …… (3)

• C₁: Average metal concentration of two duplicate determinations of the sample before test, mg/kg
• C₂: Average metal concentration of two duplicate determinations of the sample after test, mg/kg
• Note: The symbols in the original formula are doubtful due to the presence of source-text extraction ("G-9:" etc.), requires confirmation against the source standard (source-text extraction).

10.4 Corrected value of lead concentration change (mg/kg)

C corrected lead concentration = C lead concentration × 0.276 …… (4)

• The metal test piece distribution center specifies 0.276 as the lead test piece correction factor. To distinguish different batches of lead test pieces, the metal test piece serial number is A or C (* indicates metal test piece batch).
• C lead concentration: Change in lead concentration in the sample after test, mg/kg.

10. Precision

12.1 Test precision of reference oil

Judge the reliability of test results according to the following provisions (confidence level of 95%).

12.1.1 Intermediate precision ip

• 12.1.1.1 Definition: Determination of the same sample in the same laboratory using the same test method, with allowed changes in operator, measuring equipment, test bench, test engine and time. Note: Intermediate precision is a term defined in this standard under laboratory conditions, not strict repeatability.
• 12.1.1.2 Limit: Under intermediate precision test conditions, the difference between two results obtained from determination of the same sample shall not exceed the ip value in the precision evaluation table of Table 1. If only a single test result is obtained, the intermediate precision limit can also be used to calculate the measurement value range of the test result, which can be expressed as test result ± intermediate precision limit.

12.1.2 Reproducibility R

• 12.1.2.1 Definition: Single, independent test results obtained by different operators in different laboratories, using different equipment, according to the same test method on the same sample.
• 12.1.2.2 Limit: Under reproducibility test conditions, the difference between two results obtained from determination of the same sample shall not exceed the R value in the precision evaluation table of Table 1. If only a single test result is obtained, the reproducibility limit can also be used to calculate the measurement value range of the reproducibility test result, which can be expressed as test result ± reproducibility limit.

Table 1 Precision evaluation

Note 1: Sip— intermediate precision standard deviation; ip— intermediate precision limit; SR— reproducibility standard deviation; R— reproducibility limit. Note 2: The statistical data in this table are derived from the test results of reference oils TMC40 and TMC43. Note: In Table 1, the values in column SR are unclear in the source text (source-text extraction, 3.5, 29.6) and require confirmation against the source standard (source-text extraction).

12.2 Bias

This standard has not yet determined bias.

11. Report

The report format is given in Annex B (normative annex); the report formats are shown in Table B.1 to Table B.4.

• 11.1 Report the concentrations of copper, lead, and tin in the reference oil before and after the test and their changes (10.3 in clause C).
• 11.2 Report the concentrations of copper, lead, and tin in the test sample before and after the test and their changes (10.3 in clause C).
• 11.3 Report the corrected value of lead concentration in the test sample calculated using the correction factor (0.276) (10.4 in clause C corrected lead concentration value).
• 11.4 If the corrosion levels on the two surfaces of the copper strip differ, report the corrosion level according to the more severely corroded side.
• 11.5 Report the mass change of each metal test piece, mg/cm².

The report format includes:

• Table B.1 Report cover (test validity V- valid/I- invalid/N- test results not representative; number of heat baths, number of heat bath runs, heat bath position, test end date, test end time, oil product designation, formulation/standard designation, distinguishing number, etc.)
• Table B.2 Summary of test results (test oil sample characteristics, metal concentration changes, GB/T 5096 copper strip corrosion level, metal test piece sequence numbers, etc.)
• Table B.3 Detailed test results (metal concentrations before/after test, evaporation loss %, metal test piece mass change, etc.)
• Table B.4 Explanation

12. Normative references

• GB 1922—2006 Mineral spirits for paints and cleaning
• GB/T 5096 Petroleum products—Copper strip corrosion test method
• GB/T 17476 Determination of additive elements, wear metals, and contaminants in used lubricating oils and certain elements in base oils (inductively coupled plasma atomic emission spectrometry)
• ASTM E691 Practical method for conducting interlaboratory studies to determine the precision of a test method
• Reference: FS 791 in 5308 Gas turbine lubricating oil corrosion and oxidation test method

13. Source and verification

This page is an AI translation of the available Chinese method card. Human verification is pending. It is not an official translation of the standard. Check the source standard and product certificate before use.

14. Quick Q&A