GB/T 11143-2025 Test method for rust-preventing characteristics of inhibited mineral oil in the presence of water

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Card type: Test method

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

• Standard number: GB/T 11143—2025
• Chinese name: Test method for rust-preventing characteristics of inhibited mineral oil in the presence of water
• English name: Test method for rust-preventing characteristics of inhibited mineral oil in the presence of water
• Replacement relationship: replaces GB/T 11143—2008 (this document was first issued in 1989, first revised in 2008, and this is the second revision)
• Method number: Method A (using distilled water), Method B (using synthetic seawater), Method C (applicable to liquids denser than water)
• Publication/implementation: published on 2025-10-05, implemented on 2026-05-01
• Responsible committee: National Technical Committee for Standardization of Petroleum Products and Lubricants (SAC/TC280)

2. Scope of application and non-applicability

• This document describes a method for determining the rust-preventing characteristics of inhibited mineral oil in the presence of water.
• It is applicable to evaluating the rust-preventing ability of inhibited mineral oil, especially turbine oil, on iron parts when mixed with water.
• It is also applicable to other oils such as hydraulic oil and circulating oil, and to liquids denser than water.
• Not applicable: not provided in the available source.

3. Method principle

Mix 300 mL of sample with 30 mL of distilled water or synthetic seawater, completely immerse a cylindrical test steel rod in it, and stir at 60 ℃±1 ℃. The recommended test period is 24 h, and an appropriate test period may also be determined according to the requirements of both contracting parties. After the test period ends, observe the rust marks and degree of rust on the test steel rod.

4. Reagents and materials (purity / preparation)

• 5.1 Isooctane: analytical reagent.
• 5.2 Petroleum ether: analytical reagent, 90 ℃~120 ℃.
• 5.3 Distilled water: meets the grade three water requirements in GB/T 6682—2008.
• 5.4 Glassware cleaning agent: chromic acid cleaning solution or other equivalent and effective glassware cleaning agent.
• 5.5 Abrasive cloth: 150 grade (99 μm) and 240 grade (53.5 μm) or equivalent aluminum oxide abrasive cloth for metalworking.
• 5.6 Reference oil: qualified in Method A but not qualified in Method B, prepared as follows: add 0.0150% (mass fraction) of additive to white mineral oil (kinematic viscosity meets the requirements for grade 32 industrial white oil in NB/SH/T 0006), and the additive consists of 60% (mass fraction) dodecenylsuccinic acid and 40% (mass fraction) ordinary paraffinic oil (40 ℃ kinematic viscosity 19.8 mm²/s~24.2 mm²/s).
• 5.7 Synthetic seawater
  • 5.7.1 The reagents and concentrations used for synthetic seawater are shown in Table 1. Table 1 Reagents and concentrations used for synthetic seawater

    Reagent	Mass concentration/(g/L)
    Sodium chloride (NaCl)	24.54
    Magnesium chloride (MgCl₂·6H₂O)	11.10
    Sodium sulfate (Na₂SO₄)	4.09
    Calcium chloride (CaCl₂·2H₂O)	1.54
    Potassium chloride (KCl)	0.69
    Sodium bicarbonate (NaHCO₃)	0.20
    Potassium bromide (KBr)	0.10
    Boric acid (H₃BO₃)	0.03
    Strontium chloride (SrCl₂·6H₂O)	0.04
    Sodium fluoride (NaF)	0.003

  • 5.7.2 Preparation of synthetic seawater stock solutions: to avoid precipitation in high-concentration solutions, prepare stock solution No. 1 and stock solution No. 2 using chemical reagents and distilled water (5.3). Prepare the reagents used for stock solution No. 1 and stock solution No. 2 according to Table 2 and Table 3, dissolve them separately in distilled water, and dilute to 7 L. Table 2 Reagents used for stock solution No. 1

    Reagent	Mass/g
    Magnesium chloride (MgCl₂·6H₂O)	3885
    Calcium chloride (CaCl₂·2H₂O)	538
    Strontium chloride (SrCl₂·6H₂O)	14
    Table 3 Reagents used for stock solution No. 2
    Reagent	Mass/g
    ---	---
    Potassium chloride (KCl)	483
    Sodium bicarbonate (NaHCO₃)	140
    Potassium bromide (KBr)	70
    Boric acid (H₃BO₃)	21
    Sodium fluoride (NaF)	2.1

  • 5.7.3 Preparation of synthetic seawater: dissolve 245.4 g sodium chloride (NaCl) and 40.94 g sodium sulfate (Na₂SO₄) in 8 L distilled water (5.3), add 200 mL stock solution No. 1 and 100 mL stock solution No. 2, dilute to 10 L, and while stirring add 0.05 mol/L sodium carbonate solution (Na₂CO₃) until the pH value is 7.8–8.2 (about 1 mL–2 mL of sodium carbonate solution is required).

5. Apparatus and equipment

• 6.1 Liquid bath: a constant-temperature liquid bath capable of maintaining the sample temperature at 60 ℃±1 ℃. When oil is used as the bath, the oil's kinematic viscosity at 40 ℃ is 28.8 mm²/s~35.2 mm²/s. The bath vessel should have a cover, and the cover should have holes for placing the test beakers. When water is used as the bath, because water evaporates easily, pay attention to checking the water level. Note: The thermometer used to measure the sample temperature has a scale division of 0.5 ℃. In the sample, it can accurately measure 60 ℃ according to its specified immersion depth, such as thermometer No. GB-76 in GB/T 514 (equivalent to IP21C).
• 6.2 Stirrer: made of stainless steel meeting the requirements of 1Cr18Ni9Ti in GB/T 1220—2007, with an inverted "T" shape, a flat blade of 25 mm×6 mm×0.6 mm mounted on a stirring rod with a diameter of 6 mm, and the blade is symmetrical about the rod and in the same vertical plane. Note: Heat-resistant glass may also be used for the stirrer, with the same dimensions as those specified for the stainless steel stirrer.
• 6.3 Beaker: a heat-resistant tall-form beaker without a spout with a volume of 400 mL (see Figure 1), with a height (measured from the center of the inner bottom) of about 127 mm and an inner diameter of about 70 mm (measured at the middle section).
• 6.4 Beaker cover: a flat beaker cover made of glass or polymethyl methacrylate resin (PMMA), or, when testing synthetic liquids, a beaker cover made of a chemical-resistant material such as polychlorotrifluoroethylene (PCTFE). Appropriate methods, such as rims or grooves, should be used to position the cover. On any diameter of the cover, there are two holes: one hole is used to install the stirrer (6.2), the hole diameter is 12 mm, and the distance from its center to the center of the cover is 6.4 mm; the other hole is on the other side of the center of the cover and is used to place the test steel rod assembly, the hole diameter is 18 mm, and the distance from its center to the center of the cover is 16 mm. In addition, a third hole is used to place a thermometer, the hole diameter is 12 mm, the distance from its center to the center of the cover is 22.5 mm, and it is located on the perpendicular bisector of the diameter passing through the other two holes. Note: An inverted culture dish can serve as a suitable cover because the periphery of the culture dish keeps it in a fixed position; use suitable polymethyl methacrylate resin (PMMA) to make the beaker cover (as shown in Figure 2). A long hole 1.6 mm wide and 27 mm long is opened on the cover, its centerline passes through the center of the stirrer hole and is perpendicular to a diameter passing through the centers of the steel rod hole and the stirrer hole on the cover, so that the stirrer can be removed without removing the beaker cover.
• 6.5 Test steel rod: dimensions are shown in Figure 3, and the material should meet the following specifications: carbon (C): 0.15%~0.20% (mass fraction); manganese (Mn): 0.60%~0.90% (mass fraction); sulfur (S): ≤0.05% (mass fraction); phosphorus (P): ≤0.04% (mass fraction); silicon (Si): <0.10% (mass fraction). If these steels are not available, other steels that have been verified by comparison, give satisfactory results, and can prove equivalent performance may also be used.
• 6.6 Steel rod plastic handle: made of polymethyl methacrylate resin (PMMA), with dimensions as shown in Figure 3 (two types of handles are shown in the figure). When testing synthetic liquids, the steel rod plastic handle should be made of a chemical-resistant material, such as polytetrafluoroethylene (PTFE).
• 6.7 Stirring device: a suitable stirring device capable of maintaining the stirring speed at 1000 r/min±50 r/min.
• 6.8 Grinding and polishing equipment: a suitable chuck that can hold the test steel rod and a device that rotates the test steel rod at a speed of 1700 r/min~1800 r/min (see Figure 3 and Figure 4).
• 6.9 Oven: capable of maintaining the temperature at 65 ℃±1 ℃.

6. Recommended operating conditions

• Sample amount: 300 mL
• Aqueous phase: 30 mL±1 mL distilled water (method A) or synthetic seawater (method B)
• Test temperature: 60 ℃±1 ℃
• Stirring speed: 1000 r/min±50 r/min
• Recommended test period: 24 h (may also be determined as required by both contracting parties)
• Stirring rod position: 6 mm from the center of the beaker containing the sample, with the blade no more than 2 mm from the bottom of the beaker
• Thermometer immersion depth: 56 mm
• Suspension position of the test steel rod: the lower end is 13 mm~15 mm from the bottom of the beaker
• Wetting stirring: 30 min
• Inspection illuminance: ordinary light (illuminance 650 lx)

7. Sampling and specimen preparation

• Sampling: sample in accordance with the provisions of GB/T 4756.
• Specimen preparation: not provided in the available source (no dedicated specimen preparation clause other than sampling).

8. Analytical procedure

• 8.1 Two test steel rods (6.5) should be prepared for each test; they may be new or used test steel rods, and should be prepared in accordance with 8.2, 8.3 and 8.4.
• 8.2 If the test steel rods are not made of the steel described in 6.5, comparative experiments on the test steel rods are required. Test steel rods that have rusted should not be used in comparative tests. Test steel rods that repeatedly rust in tests of various oils may be defective, and these test steel rods should be placed in qualified oil for testing. If rusting still occurs in repeated tests, these test steel rods should be discarded.
• 8.3 The test steel rod assembly consists of a cylindrical test steel rod mounted on a plastic handle for the steel rod (6.6). The new cylindrical test steel rod (6.5) has a diameter of 12.7 mm and a length of about 68 mm [excluding the threaded portion screwed into the plastic handle for the steel rod (6.6)]; one end of the test steel rod is made into the taper shown in Figure 3.
• 8.4 Preliminary grinding: if the test steel rod has been used before and its surface has no rust or other unevenness, preliminary grinding may be omitted. Only final polishing as described in 8.5 is needed. If a new test steel rod (6.5) is used, or if any part of the surface of the test steel rod has rust or unevenness, first clean it with isooctane (5.1) or petroleum ether (5.2). From the time the test steel rod is cleaned with petroleum ether or isooctane until the end of the test, the test steel rod should not be touched by hand; forceps or a clean lint-free cotton cloth may be used to handle it. Then grind with 150 grade alumina abrasive cloth (5.5) to remove all unevenness, pits and scratches visible to the naked eye. Fix the test steel rod on the chuck of the grinding and polishing equipment (6.8), rotate the test steel rod at a speed of 1700 r/min~1800 r/min, and grind with used 150 grade alumina abrasive cloth (5.5) to remove rust or relatively large surface unevenness. Then complete the grinding with new 150 grade alumina abrasive cloth (5.5), and immediately perform final polishing with 240 grade alumina abrasive cloth (5.5), or remove the test steel rod from the chuck and store it in isooctane (5.1) before use. When the diameter of a used test steel rod decreases to 9.5 mm, it must not be used again.
• 8.5 Final polishing: before the test, the test steel rod (6.5) should be finally polished with 240 grade alumina abrasive cloth (5.5). If the preliminary grinding of the test steel rod has just been completed, stop the motor that rotates the test steel rod. If the test steel rod is taken out of isooctane (5.1) (used rust-free steel rods should be stored in isooctane (5.1)), wipe the test steel rod dry with a clean cloth and mount it on the chuck. Polish the stationary test steel rod longitudinally with a new piece of 240 grade alumina abrasive cloth (5.5) so that visible scratches appear over the entire surface. Then rotate the test steel rod at a speed of 1700 r/min–1800 r/min, wrap a new piece of 240 grade alumina abrasive cloth (5.5) tightly around the test steel rod for half a turn, pull the loose end of the abrasive cloth (5.5) steadily and appropriately, and continue polishing for 1 min–2 min to produce a uniform and fine polished surface without longitudinal scratches. To ensure that the flat shoulder (the part of the test steel rod perpendicular to the threaded rod) has no rust, this surface should also be polished. Place 240 grade alumina abrasive cloth (5.5) between the clamp and the flat shoulder, and rotate the test steel rod for a relatively short time to polish the surface. Remove the test steel rod from the chuck, do not touch it by hand, gently wipe it with a clean and dry lint-free cotton cloth or paper (or a camel hair brush), mount the test steel rod on the plastic handle for the steel rod (6.6), and immediately immerse it in the sample. The test steel rod may be placed directly into the hot sample (see 9.1.1), or it may first be placed in a clean test tube containing the sample, then removed from the test tube, drained slightly, and then placed in the hot sample.
• 9.1 Method A (using distilled water)
  • 9.1.1 Clean the beaker (6.3) in accordance with good laboratory cleaning procedures, rinse thoroughly with distilled water (5.3), and place in an oven (6.9) to dry. Clean the glass beaker cover (6.4) and glass stirring rod in the same way. The stainless steel stirring rod body and the polymethyl methacrylate resin (PMMA) cover should first be cleaned with isooctane (5.1) or petroleum ether (5.2), then rinsed thoroughly with hot water, finally rinsed with distilled water (5.3), and dried in an oven (6.9) at a temperature not exceeding 65 ℃±1 ℃.
  • 9.1.2 Pour 300 mL of sample into the beaker (6.3), and place the beaker (6.3) into a hole of a liquid bath (6.1) capable of maintaining the sample temperature at 60 ℃±1 ℃, fixing it by the edge of the beaker so that the beaker hangs on the liquid bath cover. The liquid level in the bath should not be lower than the oil level in the beaker (6.3). Cover with the beaker cover (6.4), install the stirrer (6.2), so that the stirring rod is 6 mm from the center of the beaker containing the sample, and the blade is no more than 2 mm from the bottom of the beaker. Insert the thermometer into the thermometer hole in the beaker cover (6.4) to an immersion depth of 56 mm. Start the stirring device (6.7), and when the temperature reaches 60 ℃±1 ℃, place the test steel rod prepared in accordance with Chapter 8. Note: when multiple samples with the same characteristics are placed simultaneously in a constant-temperature liquid bath, it is not necessary to insert a thermometer into each sample, because the constant-temperature bath can control the temperature of each beaker sample within the allowable range. When analyzing a single sample, insert the thermometer into the thermometer hole in the beaker cover to an immersion depth of 56 mm. Start the stirrer device, and when the temperature reaches 60 ℃±1 ℃, place the test steel rod. To maintain the thermal balance of the liquid bath, do not add sample to the beaker after the test has started.
  • 9.1.3 Suspend the test steel rod assembly in the sample hole in the beaker cover (6.4), so that its lower end is 13 mm~15 mm from the bottom of the beaker (6.3); either type of plastic handle for the steel rod (6.6) may be used (see Figure 3). The test steel rod should be suspended in the sample hole without any obstruction; see Figure 1 for a schematic diagram of the assembled apparatus.
  • 9.1.4 Continue stirring for 30 min to ensure that the test steel rod is completely wetted. While stirring, remove the thermometer briefly, add 30 mL±1 mL of distilled water (5.3) through the thermometer hole, allow the water to sink to the bottom of the beaker, and replace the thermometer. From the time the water is added, continue stirring at a speed of 1000 r/min±50 r/min for 24 h, and maintain the temperature of the oil-water mixture at 60 ℃±1 ℃. After 24 h, stop stirring, remove the test steel rod and drain it, then wash it with isooctane (5.1) or petroleum ether (5.2); if necessary, the test steel rod may be protected with a lacquer coating. Parallel tests should be conducted on the same sample, with two consecutive determinations, and the result of each determination should be recorded. Note: the recommended test period is 24 h, but the test period may also be longer or shorter as required by both contracting parties.
• 9.2 Method B (using synthetic seawater): the method for rust prevention performance of inhibited mineral oil in the presence of synthetic seawater (5.7) should be the same as 9.1.1~9.1.4, except that synthetic seawater (5.7) is used instead of distilled water (5.3) in the method part described in 9.1.4.
• 9.3 Method C (applicable to liquids denser than water)
  • 9.3.1 The stirring action produced by the stirrer specified in 6.2 is insufficient to achieve complete mixing of water and liquids denser than water. Clause 9.3 is intended to clarify the modifications made to the standard method for testing liquids denser than water. Unless otherwise specified, other steps and requirements are still carried out in accordance with the provisions of Chapter 1~Chapter 9. Since this method may use distilled water (5.3) or synthetic seawater (5.7), if method C is used, the report should indicate whether distilled water (5.3) or synthetic seawater (5.7) was used.
  • 9.3.2 The instrument requirements used in method C are as follows.
    • Beaker cover: the same as described in 6.4. Note: some liquids denser than water may corrode or dissolve the beaker cover and handle made of polymethyl methacrylate resin (PMMA). Therefore, when testing liquids denser than water, it is recommended to use a polychlorotrifluoroethylene (PCTFE) beaker cover and a polytetrafluoroethylene (PTFE) handle.
    • Stirrer: In addition to being the same as described in 6.2, an auxiliary blade is mounted on the stirring rod (as shown in Figure 5), made of stainless steel, with dimensions 19.0 mm×12.7 mm×0.6 mm; the position of the auxiliary blade on the stirring rod is such that its bottom edge is 57 mm from the top edge of the T-shaped blade, and the planes of the two blades are in the same vertical plane.
    • The test steel rods and their preparation are the same as described in Chapter 8.

9. Qualitative and Quantitative and Calculation Formulas

• 10.1 At the end of the test, all inspections of the test steel rods shall not use a magnifying glass and shall be conducted under ordinary light (illuminance 650 lx). Through the above inspection process, any rust spots and streaks visible to the naked eye on the test steel rods shall be considered rusted test steel rods.
• 10.2 In this test, some formulated oils may produce deposits of other colors (non-rust) on the surface of the test steel rods due to additive deposition. Since such deposits may mask the presence of rust, they need to be gently wiped off with lint-free cotton cloth or thin paper. If after wiping with lint-free cotton cloth or thin paper, the surface of the test steel rod shows red-brown color, black spots, or pits and unevenness, it is judged that rust is present. If after wiping with lint-free cotton cloth or thin paper, the color of the deposit is not red-brown or it is easily wiped off, it should not be considered rust.
• 10.3 In order to report whether a sample is acceptable or not, parallel tests shall be conducted. If at the end of the test period, neither of the two test steel rods has rust, the sample is "acceptable". If both test steel rods have rust, it shall be reported as "unacceptable". If one test steel rod has rust and the other does not, two more test steel rods shall be taken for retesting. If either of the two retested test steel rods shows rust, the sample shall be reported as unacceptable; if neither of the two retested test steel rods has rust, the sample shall be reported as acceptable. Note: When it is necessary to indicate the degree of rust, for the sake of uniformity, it is recommended to grade the degree of rust as follows: a) Light rust: limited to no more than 6 rust spots and each rust spot diameter not greater than 1 mm; b) Moderate rust: degree of rust exceeds the light rust range, but the rusted area does not exceed 5% of the surface area of the test rod; c) Severe rust: rusted area exceeds 5% of the surface area of the test steel rod.
• Calculation formula: not provided in the available source.

10. Precision

• 11 Precision and bias: There is no generally accepted method for determining the precision and bias of this method.

11. Report

• 12 The test report shall include the following contents.
  • a) Model and name of the tested product.
  • b) Test date.
  • c) Indicate which method among A, B, C is used. If method C is used, it shall be noted whether distilled water or synthetic seawater is used.
  • d) Test period.
  • e) Any deviations during the test operation shall be noted.
  • f) Test results; if necessary, the report shall indicate the grade of rust degree.

12. Reference Documents

• GB/T 1220—2007 Stainless steel bars
• GB/T 4756 Manual sampling of petroleum liquids
• GB/T 6682—2008 Water for analytical laboratory use—Specification and test methods
• NB/SH/T 0006 Industrial white oil
• References: [1] GB/T 514 Technical conditions for glass liquid thermometers for petroleum product testing

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.

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