GB/T 2433-2001 Determination of sulfate ash in additives and additive-containing lubricating oils

AI-translated method card — human verification pending. This is not an official translation of the standard. Unclear source values remain unverified; check the original standard and product certificate before use.

Card type: Test method

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

• Standard number: GB/T 2433-2001
• Chinese full name: Determination of sulfate ash in additives and additive-containing lubricating oils
• English name: Petroleum products—Lubricating oils and additives—Determination of sulphated ash
• Replacement relationship: replaces GB/T 2433—1981
• Adoption relationship: equivalent adoption of ISO 3987:1994 (original text marked cqv ISO 3987:1994)
• First publication: 1981 year

2. Scope of application and non-applicability

• 1.1 specifies a method for determining the mass fraction of sulfate ash in unused additive-containing lubricating oils and in additive concentrates used for blending lubricating oils. These additives usually contain one or more metals: barium, calcium, magnesium, zinc, potassium, sodium and tin. Elemental sulfur, phosphorus and chlorine are present in combined form.
• 1.2 lower limit of sulfate ash mass fraction 0.005%. When the sulfate ash is less than 0.02%, it is only applicable to lubricating oils containing only ashless additives.
• 1.3 is not applicable to the determination of used engine oils containing lead additives, nor to lubricating oils without additives; for these oils, GB/T 508 may be used.
• Note 1: There are indications that magnesium reacts in a different form from other alkali metals in the test; if magnesium additives are present, caution should be exercised when interpreting the data.
• Note 2: There are indications that results for samples containing molybdenum are low, because molybdenum compounds cannot be fully recovered at the ashing temperature.
• 1.4 Sulfate ash can be used to indicate the concentration of known metal-containing additives in new lubricating oils. When phosphorus is absent, barium, calcium, magnesium, sodium and potassium are converted to sulfates, and tin(IV) and zinc are converted to their oxides (see note); sulfur and chlorine do not interfere. However, when phosphorus is present together with metal additives, it is partially or completely retained in the sulfate ash in the form of metal phosphates.
• Note: Because zinc sulfate slowly decomposes to oxide at the combustion temperature specified in this method, when determining samples containing zinc, unless zinc sulfate is completely converted to oxide, variable results may be obtained.
• 1.5 involves certain hazardous materials, operations and equipment, but it is not intended to address all safety issues associated with them. Users should establish appropriate safety and protective measures before use and determine applicable management systems.

3. Method principle

Ignite the test sample and burn until only ash and carbon remain. After cooling, treat the residue with sulfuric acid and heat at 775°C until the carbon is completely oxidized. After the ash has cooled, treat it again with sulfuric acid, heat at 775°C to constant mass, and the mass fraction of sulfate ash can then be calculated.

4. Reagents and materials (purity / preparation)

• 6.1 Distilled water: meets the grade 3 water requirements of GB/T 6682.
• 6.2 Sulfuric acid: analytical reagent, mass fraction 98%. Note: Beware that sulfuric acid is strongly corrosive and has a high heat of hydration; protective clothing, gloves and a face shield should be worn when handling sulfuric acid.
• 6.3 Sulfuric acid solution (1:1): prepared by slowly adding 1 volumes of sulfuric acid to 1 volumes of water.
• 6.4 Isopropanol: analytical reagent.
• 6.5 Toluene: analytical reagent.
• 5.2.1 Filter paper: ash mass fraction not greater than 0.01%.
• 5.2.2 Low-ash mineral oil: white oil with sulfate ash below the lower detection limit of this standard. Its content is determined as follows: take 100 g of white oil, accurate to 0.5 g, place it in a platinum evaporating dish of 120 mL~150 mL, determine the sulfate ash according to the provisions of Chapter 8 of this standard method, and deduct the sulfuric acid blank as described in clause 8.11.

5. Apparatus and equipment

• 5.1.1 Evaporating dish or crucible: made of porcelain-fused silica or platinum, capacity 50 mL–100 mL; for samples with sulfate ash mass fraction less than 0.2%, use a platinum evaporating dish or crucible of capacity 120 mL–150 mL. If the sample is known to contain elements such as phosphorus that corrode platinum, platinum evaporating dishes should not be used.
• 5.1.2 Gas burner or electric furnace.
• 5.1.3 Muffle furnace: capable of heating and controlling at 775°C±25°C. Preferably has small holes at the front or rear so that air can slowly pass through the furnace by natural ventilation.
• 5.1.4 Cooler: without desiccant.
• 5.1.5 Balance: sensitivity 0.1 mg.

6. Recommended operating conditions

• Ashing/ignition temperature: 775°C (muffle furnace controlled at 775°C±25°C).
• Constant temperature holding time: 30 min (8.8).
• Evaporating dish/crucible pretreatment: heat in a muffle furnace at 775°C and hold for at least 10 min (8.2).
• Heating method: gas burner or electric furnace (5.1.2, 8.4); when heating with an electric furnace, if the sample is not ignited, filter paper may be used to ignite it (8.4 note).
• Other recommended operating conditions: not provided in the available source.

7. Sampling and test sample preparation

• 7 Sampling: unless otherwise specified, samples shall be taken in accordance with GB/T 4756.
• 8.1 Select an evaporating dish or crucible of suitable capacity according to the required amount of test sample.
• 8.2 Heat the evaporating dish or crucible in a muffle furnace at 775°C and hold for at least 10 min, cool to room temperature in a cooler, weigh and be accurate to 0.1 mg.
• 8.3 Weigh into the evaporating dish or crucible a test sample amount m₁ (g) calculated according to formula (1), accurate to 0.1 mg.
  • m₁=10/m₀ …(1)
  • Where: m₀——expected mass fraction of sulfate ash produced, %.
  • The test sample amount shall not exceed 80 g; when the sulfate ash mass fraction of the lubricating oil additive is equal to or greater than 2.00%, the sample must be diluted with 10 times its amount of low-ash mineral oil.
  • If the difference between the measured sulfate ash value and the expected value is found to exceed two times, then recalculate the test sample amount considering the first determination result and carry out a second analysis.
• 8.4 When the test sample contains too much water and foaming causes loss of components: discard that test sample, add 1 mL~2 mL of isopropanol to a new test sample and then heat; if still unsatisfactory, add 10 mL equal volumes of a mixture of toluene and isopropanol and mix thoroughly with the test sample, add several strips of filter paper to the mixture and heat together; when the filter paper begins to burn, most of the water will be removed.

8. Analysis procedure

• 8.1 Select an evaporating dish or crucible of suitable capacity according to the required amount of test sample.
• 8.2 Heat the evaporating dish or crucible in a muffle furnace at 775°C and hold for at least 10 min, cool to room temperature in a cooler, weigh and be accurate to 0.1 mg.
• 8.3 Weigh in a test sample amount m₁ (g) calculated according to formula (1), accurate to 0.1 mg (see Section 7 for details).
• 8.4 Carefully heat the evaporating dish or crucible containing the test sample on a gas burner or electric furnace until the test sample ignites and produces a flame; maintain a certain temperature so that the test sample burns uniformly and moderately; after combustion ends, continue heating slowly until no more smoke is emitted. Note: If the heating equipment is an electric furnace and the test sample is not ignited, filter paper may be used to ignite it until the test sample ignites.
• 8.5 After the evaporating dish or crucible has cooled to room temperature, add sulfuric acid drop by drop to completely wet the residue, place the evaporating dish or crucible on an electric furnace and carefully heat at low temperature, preventing splashing, and continue heating until no more smoke is emitted.
• 8.6 Place the evaporating dish or crucible in a muffle furnace controlled at 775°C and heat continuously at this temperature until the carbon is completely or almost completely oxidized.
• 8.7 Cool the evaporating dish or crucible to room temperature, add 3 drops of distilled water and 10 drops of sulfuric acid solution, shake the evaporating dish or crucible to completely wet the residue, and then heat as described in 8.5.
• 8.8 Place the evaporating dish or crucible back into the muffle furnace, control the temperature at 775°C and hold constant for 30 min, and cool the evaporating dish or crucible to room temperature in a suitable cooler. If the sample contains zinc dialkyl or dialkylaryl dithiophosphate and mixtures of these additives, a partially black residue may be formed at this stage; in this case repeat the operations in 8.7, 8.8 until a white residue is obtained.
• 8.9 Weigh the mass of the evaporating dish or crucible and residue, accurate to 0.1 mg.
• 8.10 Repeat the operations in 8.8, 8.9 until the difference between two valid weighings does not exceed 1.0 mg.
• 8.11 Blank test (when the expected mass fraction of sulfate ash produced by the test sample is not greater than 0.02%): add 1 mL of sulfuric acid to a weighed platinum evaporating dish or crucible, heat until no more smoke is emitted, then heat in a furnace at 775°C for 30 min, place in a cooler to cool to room temperature, weigh, and be accurate to 0.1 mg. If there is any ash in the sulfuric acid, the mass of sulfate ash obtained shall be corrected; the mass of ash produced by the sulfuric acid shall be subtracted from the total sulfate ash of the test sample. The mass of ash produced by the sulfuric acid is determined as follows: multiply the mass of ash produced by the 1 mL sulfuric acid blank by the total volume of sulfuric acid used. When calculating the sulfate ash mass fraction (see Chapter 9), use this corrected result m₂ (g).

9. Qualitative and quantitative determination and calculation formula

Calculate the sulfate ash A (%) in the test sample according to formula (2):

A = 100 m₂ / m₁ …(2)

Where:

• m₁——mass of test sample, g;
• m₂——mass of sulfate ash, g.

10. Precision

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

11.1 Repeatability (r) The difference between two results obtained by the same operator using the same apparatus, under the same operating conditions, on the same test material shall not exceed the following value:

• When 0.005% ≤ x ≤ 0.100%, r = 0.047 x^0.8
• When 0.11% ≤ x ≤ 25.0%, r = 0.060 x^0.78
• x is the average of the two results being compared.

11.2 Reproducibility (R) The difference between two single and independent results obtained by different operators in different laboratories on the same test material shall not exceed the following value:

• When 0.005% ≤ x ≤ 0.100%, R = 0.189 x^0.86
• When 0.11% ≤ x ≤ 25.0%, R = 0.142 x^0.76
• x is the average of the two results being compared.

Table 1 Example precision values (sulfated ash % | Repeatability | Reproducibility):

(Note: In Table 1, the original text for repeatability corresponding to 0.005 is “0.000 5”, and the doubt regarding source-text extraction requires confirmation against the source standard; the original text for repeatability corresponding to 0.010 is “0.0009”, and the doubt regarding source-text extraction requires confirmation against the source standard.)

11. Report

For samples with a sulfated ash mass fraction less than 0.02%, the result shall be accurate to 0.001%; for samples with a sulfated ash mass fraction greater than or equal to 0.02%, the result shall be accurate to 0.01%.

12. Normative References

The provisions of the following standards are incorporated into this standard by reference. Unless otherwise expressly specified in this standard, the following referenced standards shall be the currently effective editions.

• GB/T 508 Petroleum products — Determination of ash
• GB/T 4756 Petroleum liquids — Manual sampling
• GB/T 6682 Water for analytical laboratory use — Specification and test methods

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 Reference Q&A