NB/SH/T 0844-2010 Determination of corrosion and oxidation stability of turbine oils

Summary page. This page is a compiled excerpt/summary of the standard — it is not the full standard text and does not replace it. Verify every value against the official standard and the product certificate before use.

NB/SH/T 0844-2010 specifies a method for determining the ability of turbine oils to resist oxidative and corrosive degradation and their tendency to corrode various metals, using glass tubes, metal specimens and a controlled air flow at elevated temperature.

Evidence note: the content of this page was compiled from the original text of this standard held in the Origin Standard library (points marked "[to be verified]" are "[source unclear]" in the original); for individual values and current status, refer to the original pages of the standard and the product certificate.

Scope: Specifies a method for determining the ability of turbine oils to resist oxidative and corrosive degradation and their tendency to corrode various metals. Petroleum-based and synthetic lubricating oils such as hydraulic oils may be used with this standard as required, selecting test conditions such as moist or dry air, with or without metal specimens, for evaluation. 1.2 The test conditions may be varied and set according to the requirements of the oil specification; if test conditions different from those of this standard are used (such as test temperature, test time, air flow, humidity, sampling frequency, sample amount and metal specimens), this shall be noted in the report. 1.3 SI units are used. 1.4 This standard involves hazardous materials, operations and equipment, but is not intended to offer advice on safety issues; users should establish appropriate safety and protective measures before use and determine the applicability of relevant regulatory limits. Not applicable: no explicit not-applicable clause is provided in the available material.

Principle: The square test metal specimens are tied together and placed in a test tube containing 100 mL of test sample; air is passed in at a flow of 5 L/h at the specified test temperature, and no sampling is carried out during the test (note: different oil specifications may require different air flow rates; if used, this shall be noted in the report). 3.2 The glass tube containing the sample and metal specimens is placed in a constant-temperature heating bath and maintained for the specified time under a flow of air with agitation; the heating bath temperature range is usually 100 °C–360 °C. The metal specimens are weighed before the test; the corrosiveness of the sample is determined by metal mass loss and by microscopic observation of the metal surface; after the test, the change in viscosity and the change in acid value of the sample are determined as measures of oil oxidation. 3.3 The metals used are: copper, steel, aluminium, magnesium and cadmium; if other metals are used, this shall be noted in the report. 3.4 No sampling is required during the whole test; after the test, the viscosity and acid value of the sample are determined and compared with the data before the test. 3.5 After the test, the amount of sludge in the test tube is determined after centrifugation, and the sample mass loss during the test is determined by weighing. 3.6 Dry air is used; if moist air is required, air of the required humidity may be supplied through a humidity conditioner.

Apparatus: Glassware: consisting of the following standard thick-walled borosilicate glassware, construction as shown in Figures 1–5. 5.1.2 Sample tube head (optional): see Figure 2. 5.1.3 Air tube: see Figure 3. 5.1.4 Condenser: see Figure 4; if the sample tube head is not used, a condenser with a 71/60 joint may be used. 5.1.5 Equipment assembly drawing: the assembly drawing when the sample tube head is used is shown in Figure 5; the combined tube consists of the sample tube, sample tube head and air tube, and contains the sample and metal specimens; when the sample tube head is not used, the combined tube consists of the sample tube and air tube and contains the sample and metal specimens in the sample tube. 5.2 Other mounting components: PTFE, 10/18 joint, to seal the gap between the air tube and the sample tube head. 5.3.1 Heating bath: control accuracy is [source unclear] missing at this point in the original ([to be verified] ([source unclear])); immersion depth 250 mm ± 20 mm; an oil bath or aluminium bath is recommended, and above 220 °C an aluminium bath or other non-oil heating medium shall be used (warning: the surface of the heating equipment is extremely hot; protective equipment shall be used as required to avoid bare skin contact with the heating equipment surface). 5.3.2 Exhaust hood: sufficient to remove fumes generated during heating. 5.3.3 Gas supply: free of active substances, dew point not higher than −68 °C; for moist air, humidity under standard conditions (21 °C, 105 kPa) of 10 mg water/L air ±1 mg water/L air ([source unclear]). 5.3.4 Flowmeter: range 10 L/h ±1 L/h under standard conditions ([source unclear]). 5.3.5 Analytical balance: sensitivity 0.1 mg. 5.3.6 Laboratory balance: range 0–2500 g, sensitivity 0.1 g. 5.3.7 Centrifuge: capable of ensuring a relative centrifugal force of 840 ± 40 at the end of the tube. 5.3.8 Centrifuge tube: conical tube conforming to GB/T 11414, 100 mL. 5.3.9 Microscope: magnification 20×. 5.3.10 Thread or wire: for tying the metal specimens; linen thread, cotton thread, nylon thread or ceramic fibre may be used; the wire may be nickel-chromium-iron alloy wire or tantalum wire. 5.3.11 The air shall be treated to meet the conditions specified in 5.3.3; if drying is required, the air may be passed through a glass column of suitable diameter packed with anhydrous calcium sulfate particles not larger than 2360 μm, with an air flow rate not greater than 1.2 m/min; if humidification is required, the method given in Annex A may be used. 5.3.12 Oven: conventional, capable of drying glass bottles at high temperature. 5.3.13 Tweezers: stainless steel. 5.3.14 Thermocouple (optional): sheathed thermocouple approximately 70 cm long. 5.3.15 Brush: stiff pig bristle (a printer cleaning brush or similar brush is acceptable).

Reagents and reference materials: Reagent purity: analytical grade chemicals are required for all tests; if reagents of other grades are used, their purity shall be such that it does not reduce the accuracy of the test. 6.1.1 Water: unless otherwise specified, shall conform to GB/T 6682; for arbitration, grade 2 water as specified in GB/T 6682 is required. 6.1.2 n-Heptane (warning: flammable, harmful if inhaled). 6.1.3 Acetone (warning: extremely flammable, vapour may cause flash explosion). 6.1.4 Concentrated nitric acid (warning: toxic, corrosive, strong oxidizer). 6.1.5 Degreasing solvent: n-heptane or toluene. 6.1.6 Glassware carbon removal agent: a mixture of 35 mL of saturated sodium dichromate aqueous solution and 1000 mL of concentrated sulfuric acid (warning: corrosive). 6.1.7 Metal specimen cleaning solution: a mixture of equal amounts of 15 g/L sodium hydroxide (NaOH) aqueous solution and 15 g/L sodium phosphate (Na₃PO₄) aqueous solution (warning: corrosive). 6.1.8 Desiccant: anhydrous calcium sulfate. 6.2.1 Square metal specimens: thickness 0.81 mm, dimensions 25.4 mm × 25.4 mm, material conforming to the corresponding provisions of ASTM DS-561, see Table 1. Table 1 Specification of metal specimen material composition | Material | Composition, % | |---|---| | Magnesium alloy M11311 | Mg balance; Al 2.5–3.5; Zn 0.6–1.4; Mn ≥0.2; Si ≤0.10; Ca ≤0.04; Fe ≤0.005; Ni ≤0.005; Cu ≤0.05; total other impurities ≤0.30 | | Aluminium alloy A92024 | Al balance; Ti ≤0.15; Zn ≤0.25; Mn 0.30–0.9; Si ≤0.5; Mg 1.2–1.8; Fe ≤0.50; Cr ≤0.1; Cu 3.8–4.9; total other impurities 0.15, each ≤0.05, Ti+Zr ≤0.2 | | Electrolytic copper C11000 | Cu ≥99.90 | | Cadmium L01900 | Cd 99.90; Zn ≤0.035; Ag ≤0.01; Cu ≤0.015; Pb ≤0.025; As ≤0.003; Sb ≤0.001; Sn ≤0.01; other impurities Ti ≤0.003 | | Carbon steel G10100 | Fe balance; Mn 0.30–0.60; C 0.08–0.13; S ≤0.050; P ≤0.03 | 6.2.2 Abrasive paper: emery of various grades conforming to JB/T 7498, including P240 and P400; abrasive papers of the "wet and dry", "waterproof" or natural emery containing iron abrasive types should not be used. 6.2.2.1 Silicon carbide particles: P150. 6.2.3 Absorbent cotton.

Key conditions: Test temperature: heating bath temperature adjusted to 175 °C ± 0.5 °C (10.7; the original value is [source unclear], printed as "175" followed by an illegible character and "+9.5%", [to be verified] ([source unclear])). Air flow: 5 L/h ± 0.5 L/h (10.13). Sample amount: 100 mL ± 1 mL (8.3, 10.4). Immersion depth: 250 mm ± 20 mm (10.10). Condenser water temperature: 18 °C ± 3 °C (10.11). Heating bath temperature range is usually 100 °C–360 °C (3.2). Test time: no specific value is provided in the available material (determined by the oil specification requirements). Air humidity: dry air or moist air (10 mg water/L air ±1 mg water/L air under standard conditions of 21 °C, 105 kPa, [to be verified] ([source unclear])).

Calculation and results: Percentage mass loss of the sample M%: M% = (m₂ − m₄)/(m₂ − m₁) × 100 (1) where: m₁—sum of the initial masses of the sample tube and the sample before the test, g; m₂—mass of the combined tube before the test, g; m₄—mass of the combined tube after the test, g. 11.2 Change in sample viscosity V%: V% = (V − V₀)/V₀ × 100 (2) where: V₀—kinematic viscosity of the sample before the oxidation test, mm²/s; V—kinematic viscosity of the sample after the oxidation test, mm²/s. 11.3 Change in sample acid value: C = T − T₀ (3) where: T₀—acid value of the sample before the oxidation test, mgKOH/g; T—acid value of the sample after the oxidation test, mgKOH/g. 11.4 Change in metal specimen mass D, mg/cm²: D = (m₃ − m₅)/A (4) where: m₃—mass of the metal specimen before the oxidation test, mg; m₅—mass of the metal specimen after the oxidation test, mg; A—area of the metal specimen (side area not considered), cm². 11.4.1 Metal specimen area: A = 2LW (5) where: L, W—the two side lengths of the metal specimen, to the nearest 0.1 cm. Qualitative determination: the corrosiveness of the metal specimens is determined by metal mass loss and by microscopic observation of the metal surface (3.2); report whether the cleaned metal specimen shows pitting, scratching or other corrosion marks (12.4).

Quality control: Precision: because there are insufficient test data, precision has not yet been established for this standard. 13.2 Bias: because no suitable reference material is available for the procedure for determining the bias of test results for the corrosion and oxidation stability of turbine oils in this standard, the bias cannot be determined for this standard.

Normative references: GB/T 265 Petroleum products — Determination of kinematic viscosity and calculation of dynamic viscosity GB/T 6682 Water for analytical laboratory use — Specification and test methods (GB/T 6682-2008, ISO 3696:1987, MOD) GB/T 7304 Petroleum products and lubricants — Determination of acid value (potentiometric titration method) GB/T 11414 Laboratory glassware — Bottles (GB/T 11414-2007, ISO 4796-1:2000, ISO 4796-2:2000, ISO 4796-3:2000, MOD) JB/T 7498 Coated abrasives — Abrasive paper ASTM DS-561 Unified numbering system for metals and alloys ASTM D4636-99 (2004) Standard test method for determination of corrosion and oxidation stability of hydraulic oils, aviation turbine engine oils and other deeply refined lubricating oils (source standard, modified adoption)

Evidence note: [to be verified] and [source unclear] mark specific points that still require checking against the original text of the standard and do not indicate that they have been verified. Do not use these values or steps directly as a basis for work.

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