GB/T 391-1977 Determination of corrosiveness of engine 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 title / English name / replacement relationship

• Standard number: GB 391-77 (confirmed in 1988)
• Chinese title: Determination of corrosiveness of engine lubricating oils
• English title: Engine lubricating oils — Determination of corrosivity (original spelling is "Iubricatlng olls", "comroslvity", requires confirmation against the source standard (source-text extraction))
• Replacement relationship: replaces GB 391-64
• Issued/implemented: issued by the National Bureau of Standards and Metrology 1977-11-08, implemented 1978-01-01

2. Scope of application and non-applicability

• Applicable to the determination of the corrosiveness of engine lubricating oils (the original text contains only this one sentence).
• Non-applicable scope: not provided in the available source.

3. Method principle

• The metal corrosion phenomenon caused when the hot lubricating oil film adhering to the surface of the metal sheet comes into periodic contact with oxygen in the surrounding air.
• After the metal sheet is kept in the sample heated to 140℃ for 50 hours, the corrosiveness of the sample is determined from the change in mass of the metal sheet, expressed in grams per square meter.
• Unless otherwise specified, the metal sheet material is lead.

4. Reagents and materials (purity / preparation)

• Benzene: analytical reagent grade.
• Mineral oil: open-cup flash point not lower than 250℃, used as the oil bath.
• Industrial filter paper.
• Lead sheet: dimensions 20×45×1.5~4 millimeters, using lead conforming to GB 469-64 "Lead — Classification and technical conditions" standard, grade Pb-3 or Pb-4; each lead sheet has a hole with a diameter of 2 millimeters, with the center of the hole located 5 millimeters from the edge at 20 millimeters and 10 millimeters from the edge at 45 millimeters; each lead sheet can be used for only one test.
• Unbleached thread (used to hang the lead sheet on the hook).
• Preparation method: not provided in the available source.

5. Apparatus and equipment

• Apparatus for determining the corrosiveness of engine lubricating oils (see figure).
• Test tube: length 270±1 millimeters, inner diameter 30±1 millimeters, made of hard glass, each test tube should be engraved with a number (original text "2701 millimeters" "301 millimeters" requires confirmation against the source standard (source-text extraction)).
• Steel wire hook: diameter 1.2–1.5 millimeters, length 190–210 millimeters, with hooks at both ends, used to suspend the metal sheet and to hang on the moving ring 9; the shape of the hook and the length of the steel wire should be such that each suspended metal sheet is located in the center of the test tube immersed in the oil bath, and when the motor is started, the upper edge of the metal sheet can be 25~30 millimeters above the edge of the test tube.
• Porcelain evaporating dish: used for washing the metal sheet.
• Temperature regulator: capable of maintaining the temperature in the oil bath at 140±2℃; a rheostat may be used instead.
• Mercury thermometer.
• Medium-size goat-hair brush.
• Instrument structure (figure captions): 1— motor; 2— jaw clutch; 3— worm reduction gear; 4— conduit; 5— shaft; 6— paddle; 7— crank; 8— connecting rod; 9— moving ring; 10— oil bath; 11— oil bath cover; 12— oil bath jacket; 13— test tube socket; 14— cylinder.

6. Recommended operating conditions

• Oil bath temperature: 140~142℃ (during the test, use a temperature regulator or rheostat to maintain the oil bath temperature at 140±2℃).
• Number of times the metal sheet is immersed in the sample: 15~16 times per minute.
• Test duration: 50 hours.
• Sample amount: 80±1 grams per portion (original text "801 grams" requires confirmation against the source standard (source-text extraction)), weighed to the nearest 0.1 grams.
• Weighing precision: weighed to the nearest 0.0002 grams.

7. Sampling and sample preparation

• Use two metal sheets for each sample test.
• The lead sheet is only wiped gently with filter paper; if the surface of the lead sheet is uneven, it may be filed flat with a file, then wiped until both sheets are equally bright.
• Engrave a number on each metal sheet with a needle tip, measure its area, then place it in a porcelain evaporating dish containing benzene and gently brush it with a medium-size goat-hair brush until the benzene used for washing leaves no stain after evaporation on filter paper.
• After washing with benzene, dry each metal sheet with filter paper, and after 2~3 minutes weigh to the nearest 0.0002 grams.
• The sample should be mixed uniformly before weighing.

8. Analytical procedure

1. Connect the power supply of the oil bath electric heater and the motor, so that the oil in the bath is heated to 140~142℃ under stirring.
2. In a pre-weighed clean and dry test tube, weigh two portions of uniformly mixed sample, 80±1 grams each, weighed to the nearest 0.1 grams.
3. Turn off the motor, stop stirring the oil bath, and immerse the test tube containing the sample through the socket into the oil bath preheated to 140~142℃. Suspend the metal sheets prepared according to 4.1 and 4.2 above the center of each test tube.
4. After the metal sheets are properly suspended, start the motor and record the time (the test start time is counted from when the motor is started). When the motor is started, all metal sheets suspended on the moving ring should fall simultaneously into the heated sample, and then the metal sheets are lifted into the air, so that the hot sample film periodically contacts oxygen in the air. The number of times the metal sheet is immersed in the sample should be 15~16 times per minute. Maintain the oil bath temperature at 140±2℃ throughout the test.
5. After the test reaches 50 hours, turn off the motor and the electric heater, remove each metal sheet from the sample, and wash with benzene according to clause 4.2. After drying each metal sheet with filter paper, weigh to the nearest 0.0002 grams, and determine its mass change.

• Note: If laboratory operating conditions do not permit continuous testing for 50 hours, intermittent testing is allowed, but the total test time is still 50 hours. When the test is interrupted, turn off the motor and the electric heater, remove the metal sheets, wash with benzene, dry with filter paper, and place in a desiccator. Remove the test tube containing the sample from the oil bath, cool it, and stopper it with a cork. When resuming the test, according to clauses 4.3, 5.2 and 5.3, hang each metal sheet back above the original test tube. For arbitration testing, the 50-hour test must be carried out continuously.

9. Qualitative and quantitative determination and calculation formula

• Calculate the total area of the six faces of the metal sheet, expressed in square meters.
• The corrosiveness of the sample X (grams per square meter) is calculated according to the following formula: X = G / F Where: G— mass change of the metal sheet after the test, grams; F— total area of the metal surface, square meters. (The original formula is typeset as "x-ma"; the symbol correspondence requires confirmation against the source standard (source-text extraction))

10. Precision

The difference between two results of repeated determination should not exceed the following values:

11. Report

Take the arithmetic mean of the two results of repeated determination as the corrosiveness of the sample.

12. Referenced documents

• GB 469-64 "Lead — Classification and technical conditions" (cited in the original text, used for lead sheet material Pb-3 or Pb-4).

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