SH/T 0650-1997 Test method for rust-preventing characteristics of metal protectives (humidity cabinet method)

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Card type: Test method

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

• Standard number: SH/T 0650-1997
• Chinese title: Test method for rust-preventing characteristics of metal protectives (humidity cabinet method)
• English title: Standard test method for rust protection by metal preservatives in the humidity cabinet
• Replacement relationship: not provided in the available source (no replacement of any standard is mentioned)
• Adoption relationship: equivalent adoption of ASTM D1748-83(1993) "Determination of rust-preventing characteristics of metal protectives in a humidity cabinet"
• Approval/implementation: approved by China Petrochemical Corporation 1997-10-27, implemented on 1998-07-01; confirmed in year (20□□) (year requires confirmation (source-text extraction))
• Responsible body: Research Institute of Petroleum Processing, China Petrochemical Corporation
• Drafting unit: Dalian Petrochemical Company, Sinopec
• Drafters: Xu Ping, Yang Jiexian

2. Scope of application and non-applicability

• 1.1 specifies a method for evaluating the rust-preventing characteristics of metal protectives under high humidity.
• 1.2 is applicable to metal protectives.
• 1.3 involves certain hazardous materials, operations and equipment, but does not purport to address all safety problems; users should establish appropriate safety and protective measures before use and determine applicable management systems.
• 4.1 When high humidity is not the main factor causing corrosion, this standard cannot be used to judge the effectiveness of metal protectives.
• 4.2 is limited to comparison between the same type of metal protective used for the same purpose.
• 4.4 The results obtained by this test only eliminate the most unsuitable materials or indicate the ranking order of rust-preventing performance under high humidity; it neither specifies the exposure period for using the product nor performs data processing on the experimental results.

3. Method principle

Immerse a test specimen cleaned according to the specified requirements into the sample, then take out the test specimen so that the sample drains off, and place it in a humidity cabinet at 49℃±1℃, suspending it until the specified test time. The rust-preventing performance of the sample under high humidity is judged according to the number and size of rust spots on the surface of the test specimen. Note: During the test, the temperature in the humidity cabinet may be the temperature specified in the product standard.

4. Reagents and materials (purity / preparation)

4.1 Reagents

• 6.1.1 Petroleum ether: 60～90℃, analytical reagent.
• 6.1.2 Anhydrous ethanol: analytical reagent.

4.2 Materials

• 6.2.1 Precipitated petroleum ether: complies with the provisions of "Quality requirements for precipitated petroleum ether" in SH/T 0024.
• 6.2.2 Alumina abrasive cloth: grain size No. 240.
• 6.2.3 Silica sand: white, dry, sharp, free of chlorine or alumina [its size shall be such that 100% passes through sieve No. 10 (2.00 mm), at least 90% passes through sieve No. 20 (850 μm), and at most 10% passes through sieve No. 50 (300 μm)].
• 6.2.4 Absorbent cotton or medical gauze.

4.3 Requirements for water in the humidity cabinet (7.1)

• Water level: 203 mm ± 6 mm
• pH value: 5.5～7.5
• Oil content: clean, oil-free
• Chloride: < 0.002% (according to GB/T 11896)
• Sulfate and sulfite: calculated as sulfate, < 0.002% (according to GB/T 11899)
• Note: Before the sulfate test, take a water sample and azeotrope with 10 mL bromine-saturated water.
• Cover: must be closed tightly
• Cloth layer on the cover: must not be folded, contaminated, or contain water droplets
• Opening the cover: open the front part of the cover to a height of 355 mm

5. Apparatus and equipment

• 5 Apparatus: detailed technical requirements for the apparatus are given in Annex A.
• Annex A (normative annex) Technical requirements for the humidity cabinet:
  • A1 Location: the location of the humidity cabinet must ensure that the test can be operated and controlled continuously. The humidity cabinet should be placed in a room at a temperature of 24℃±5.5℃. The room should have no strong ventilation and must not be exposed to acid mist or gases that can cause corrosion, such as sulfur dioxide, hydrogen sulfide and ammonia, etc.
  • A2 Humidity cabinet: composed of a test specimen rotating rack, air delivery device, temperature regulation and control device, filter and gas flowmeter, etc.
    • A2.1 Temperature inside the cabinet: 49℃±1℃ (the test may be conducted at the temperature specified in the product standard).
    • A2.2 Relative humidity inside the cabinet: above 95%.
    • A2.3 Air delivery: air flow rate is 0.8 m³/h±0.03 m³/h (original unit requires confirmation (source-text extraction)). The air entering the cabinet passes through a filter (a filter of activated carbon and glass wool or a filter of other materials) to remove dust or grease and other contaminants, then enters the cabinet and passes through a water layer at the bottom of the cabinet with a depth of 200 mm into the test specimen exposure area (depth unit requires confirmation (source-text extraction)).
    • A2.4 The pH value of the water layer at the bottom of the cabinet is 5.5～7.5.
    • A2.5 The spacing between specimen hanging slots on the test specimen rotating rack is not less than 35 mm.
    • A2.6 Rotation speed of the test specimen rack (speed at full load) is 0.33 r/min±0.03 r/min.
    • A2.7 The cabinet cover uses two layers of thick cloth to ensure that air can freely enter and leave the cabinet; condensed water droplets must not fall on the test specimens; the sample draining from the test specimens should be received in an oil pan and must not contaminate the water layer at the bottom.
    • A2.8 The humidity cabinet is made of corrosion-resistant material.
  • A3 Test specimens:
    • A3.1 Only test specimens meeting the following requirements may be used:
      • (1) The test specimen dimensions are 51 mm×102 mm×(3.0～3.4)mm, with two holes of diameter 2.3～3.2 mm on the side near the 102 mm edge (as shown in Figure A1), and the distance from the center of the holes to both sides is 1.8～2.0 mm. The mass of the test specimen is 110 g±15 g (original text "11081 15g" requires confirmation (source-text extraction)).
      • (2) The test specimen material complies with the requirements of GB/T 711 (cold-rolled) high-quality carbon structural thick steel plate and wide steel strip.
      • (3) All edges of the test specimen must be rounded, and the surface must have no pitting, scratches, corrosion or other defects.
    • A3.2 After processing, the test specimens must be immediately coated with a non-volatile water-soluble rust preventive and stored in waterproof packaging.
  • A4 Blank test specimens: the empty positions left after hanging test specimens on the turntable are filled with blank test specimens. The blank test specimens are made of stainless steel, and their dimensions are the same as those of the test specimens.
  • A5 Hooks: made of stainless steel wire with a diameter of 1.2 mm. The design must prevent condensed water on the hooks and turntable from flowing onto the test specimens, and allow it to drain off at the curved part of the hook. To insulate the test specimens from the humidity cabinet, an insulating tube of about 25 mm is fitted on the end of the steel wire and hung on the turntable.
  • A6 Additional equipment:
    • A6.1 Surface finish measuring instrument or other suitable instrument: used to periodically inspect the surface finish of the test specimens. The effective area of the test specimen is shown in Figure A1.
    • A6.2 Fluorescent lamp with lampshade (12 W): the test specimen should preferably be 305 mm away from the light source. A magnifying glass may be used to inspect the test specimens, but when judging the rusted area, a magnifying glass must not be used.

6. Recommended operating conditions

• Temperature inside the humidity cabinet: 49℃±1℃ (the test may be conducted at the temperature specified in the product standard).
• Relative humidity inside the humidity cabinet: above 95%.
• Air flow rate: 0.8 m³/h±0.03 m³/h (unit requires confirmation (source-text extraction)).
• pH value of the water layer at the bottom of the cabinet: 5.5～7.5.
• Rotation speed of the test specimen rack (full load): 0.33 r/min±0.03 r/min.
• Temperature of the room where the humidity cabinet is placed: 24℃±5.5℃.
• Heating temperature of the sample: 23℃±0.5℃.
• Draining temperature: 24℃±3℃ (original text "249C±3℃" requires confirmation (source-text extraction)), leave for 2 h±20 min.
• After oil immersion, the temperature control shall not exceed 27℃; if it exceeds 27℃, immerse the next test specimen in the second oil storage beaker at 23℃±0.5℃.
• Open the humidity cabinet twice a day: (1) once at 15 min; (2) after the first opening, open at 5 min after an interval of at least 3 h (preferably an interval of 6～8 h, combined with checking the operating conditions).

7. Sampling and test specimen preparation

7.1 Humidity cabinet preparation

Before evaluating the sample, the humidity cabinet must be operated continuously according to the requirements specified in Annex A, and the water in the cabinet must meet the requirements of 7.1 (see Section 4 4.3).

7.2 Preparation of test specimens

• 7.2.1 Select test specimens meeting the provisions of A3 in Annex A, place the test specimens in a beaker and wash off the preservative with petroleum ether. Carefully observe each test specimen. To distinguish the test specimens, a number may be engraved on the lower right corner of the outer edge of the effective area of the test specimen, or after the test specimen is polished, a small metal piece may be tied to the outer hook as a mark.
• 7.2.2 Surface treatment — grinding method:
  • 7.2.2.1 Grind the test specimen with alumina abrasive cloth (sandpaper or iron oxide abrasive must not be used); the grinding time should be short, but a high-speed belt grinder must not be used because the frictional heat it generates can change the surface properties of the test specimen.
  • 7.2.2.2 During grinding, place the test specimen in a clean and dry place, with clean filter paper of appropriate thickness underneath to prevent contamination. Line the test specimen with filter paper to prevent the test specimen from contacting fingers, then hold it by hand, or use a wooden block with a depth of 1.6 mm and an area slightly larger than the test specimen 51 mm×102 mm, and embed the test specimen in the middle. Place No. 240 alumina abrasive cloth on the palm, press the test specimen with fingers and grind back and forth, or use a wooden block, wrap the abrasive cloth around it and grind the test specimen steadily, so as not to leave grinding marks on the edges of the test specimen.
  • 7.2.2.3 During polishing, the force must be even and must be parallel to the wide edge of 102 mm; the applied force should be about 4.5～8.9 N, the direction must be straight, and each stroke must be polished to the end, so as to avoid scratching the surface. During polishing, fix the test specimen and move only the abrasive cloth; after several strokes, observe the abrasive cloth. If the abrasive cloth is already worn, turn it over and use the other side, and continue polishing until the entire surface has been freshly polished. After polishing, the finish of the test specimen is required to be 0.25～0.5 μm (the original text “0.25[unreadable separator]0.511,m” requires confirmation against the source standard (source-text extraction)). Observe the surface comprehensively; if there are scratches or other defects, continue polishing until the requirements are met. Unless it is specified that only one face of the test specimen is to be used, polish the back face in the same way.
    • Note: The polished test specimen is best measured with a surface finish meter so as to obtain the required surface finish. Once the operating technique has been mastered, visual observation can be used to compare with the test specimen surface.
  • 7.2.2.4 Use absorbent cotton dipped in petroleum ether to wash away the dust and debris from polishing. Finally, wipe the test specimen with clean absorbent cotton until no more stains are left when wiping with fresh absorbent cotton. Use a wash bottle to rinse the dust and debris out of the holes. When the test specimen has been completely cleaned, immerse the entire test specimen in anhydrous ethanol at room temperature.
    • Note: The test specimen must be regularly checked for surface cleanliness by the following method: place the clean test specimen directly on a stable, ventilated workbench, set up a burette above it so that the tip of the burette is 300 mm from the test specimen, fill the burette with distilled water, and adjust the drops so that each drop is 0.05 mL±0.01 mL; when the surface of the test specimen is completely clean, the diffusion area of the water drops at different positions on the test specimen is basically the same. A completely clean test specimen surface can cause 0.05 mL of distilled water to spread to 21～23 mm (the original text “21[unreadable separator]23-” requires confirmation against the source standard (source-text extraction)). Test specimens that have been checked should not be used for rust-prevention tests.
  • 7.2.2.5 In order to avoid affecting the test results due to different standing times in air, the polishing and cleaning of test specimens must be completed within a short time, and the operation must be carried out according to 7.2.2.2～7.2.2.4, treating the specimens one by one. The treated test specimens should immediately be immersed in anhydrous ethanol at room temperature (immersion time <2 h). The times for preparing, immersing, and draining the test specimens should be arranged to coincide exactly with the time when the humidity cabinet is about to be opened.
• 7.2.3 Surface treatment—sandblasting method:
  • 7.2.3.1 Sandblast the surface of the test specimen with a sandblasting material (silica sand or aluminum oxide) so that it becomes fresh and uniform (the recommended force of the sandblasting equipment is 178～356 N, and the distance from the test specimen to the nozzle is 51～76 mm).
  • 7.2.3.2 Immediately after sandblasting, place the test specimen into a beaker containing anhydrous ethanol or an ultrasonic cleaner containing anhydrous ethanol.
  • 7.2.3.3 Heat the anhydrous ethanol so that when the test specimen is removed from the solvent, the solvent on the test specimen can immediately evaporate.
  • 7.2.3.4 Place the test specimen on a rack at an angle of 20° to the vertical, rinse the residue on the test specimen from top to bottom with petroleum ether, and repeat the rinsing of all faces of the test specimen.
  • 7.2.3.5 Continue cleaning the test specimen successively with warm petroleum ether and hot anhydrous ethanol, then place it in a desiccator to cool.
  • 7.2.3.6 After the test specimen has been prepared, it must be used on the same day.

8. Analysis steps

• 8.1 Heat the sample to 23℃±0.5℃, then pour it into a clean, dry 500 mL glass beaker, with a height at least above 114 mm (about 375 mL). Three test specimens are required for each sample. Use a clean hook to remove the test specimen from the anhydrous ethanol solution, hang it in boiling precipitated petroleum ether vapor for 5 min, and it must be ensured that the test specimen is completely wetted by the refluxing solvent.
  • Note: When cleaning with precipitated petroleum ether vapor, 100 mL of precipitated petroleum ether may be placed in a 1000 mL heat-resistant glass beaker or metal cup, and the above steps carried out in a fume hood.
• 8.2 Place the test specimen in boiling anhydrous ethanol and clean it for 10 s, then remove it and carefully observe whether the surface of the test specimen has stains, with special attention to whether the hook hole has been cleaned. If stains still remain, reprocess the test specimen as specified in 7.2. Remove the cleaned test specimen, leave it in air for 10～20 s, then immerse it in the sample and stir for 10 s. Remove the test specimen and allow the oil to drain for 10 s; then place it into the sample again and stir gently for 1 min; within 2～4 s, remove the test specimen from the sample, preventing shaking and impact. Immerse the lower end of the hook of the second test specimen into the sample and hook it into the second hole of that test specimen; use two hooks to suspend the test specimen in a dry, clean place, and leave it at a temperature of 24℃±3℃ for 2 h±20 min so that the sample drains dry. Several test specimens may be immersed for each sample. It is only necessary to control the temperature not to exceed 27℃. If the temperature exceeds 27℃, immerse the next test specimen in the second oil-containing beaker of 23℃±0.5℃.
  • Note: The speed of removing the test specimen from the sample with the hook and the oil-draining time may be determined according to the specific use of the metal protective agent. For some samples with a very high content of metal protective agent, solvent may be used for dilution; the removal speed of the test specimen is 102 mm/min, and the oil-draining time may be as long as 24 h±1 h.
• 8.3 At the end of oil draining, hang the test specimen in the humidity cabinet (see Appendix A), with the numbered side facing forward. Leave the test specimen treated with the sample in the humidity cabinet for a certain time as required.
• 8.4 Maintain the operating conditions as described in 7.1, and every morning and afternoon after the start of the test, check and adjust the air flow rate, air temperature, pH value, and water level of the air entering the humidity cabinet. Other specified conditions are checked once a week; pH test paper may be used to determine the pH value.
  • Note: When the pH value exceeds the specification, it indicates the presence of external contamination, and analysis and correction are required. If the pH value is always low and sulfate is detected, it proves that the incoming air is contaminated by sulfur oxides. In this case, the water in the cabinet must be replaced, and an alkaline wash bottle must be connected to the air inlet system.
• 8.5 Open the humidity cabinet twice each day as follows:
  • (1) once for 15 min;
  • (2) after at least an interval of 3 h from the first opening (preferably an interval of 6～8 h, combined with checking the operating conditions), open for 5 min. In general, it is more convenient to observe the test specimens during the opening time of 15 min and to place new test specimens during the opening time of 5 min. In order to standardize the operation and avoid the influence of cooling of the test specimens or other changes, the time for observation or placing new test specimens should be minimized as much as possible, and opening should be carried out according to the above provisions. The opening position of the front cover must be fixed.
• 8.6 Inspect the test specimens according to the time specified in the product standard; during inspection, except for the last time, do not remove the test specimens from the humidity cabinet at other inspection times. Test specimens used to determine the rusting time of the metal protective agent must be removed carefully, and one test specimen should be observed at a time. Except during the specified inspection times each day, the test specimens must not leave the humidity cabinet.

9. Qualitative and quantitative determination and calculation formulas

• 9.1 After the test is completed, remove the test specimens and clean them with petroleum ether. Within 10 min, place each test specimen under a fluorescent lamp and observe the two test faces according to the effective area shown in Figure A1.
  • Pass—there are no more than three rust spots on one face of the test specimen, and the diameter of any single rust spot is not greater than 1 mm.
  • Fail—there is more than one rust spot with a diameter greater than 1 mm on one face of the test specimen, or there are four or more rust spots of any size.
• 9.2 If two of the three test specimens pass or fail, the sample may be rated as pass or fail. If there are other situations, the test must be redone.
• Calculation formula: not provided in the available source.

10. Precision

Not provided in the available source (this standard does not adopt the content of the ASTM D1748-83(1993) precision chapter; 4.3 mentions that “the precision of this standard is lower than required; for each type of metal protection, repeated tests are needed to determine its test life, and sometimes several humidity cabinets are needed for testing”).

11. Report

The report includes the following contents:

• a) Time in the humidity cabinet (h);
• b) Number of test faces (or test specimens);
• c) Test faces (or test specimens) that passed;
• d) Type of test specimen treatment (sandblasting or polishing);
• e) The test temperature specified by the product standard other than 49℃±1℃.

12. Normative references

• GB/T 711 High-quality carbon structural thick steel plate and wide steel strip (cold-rolled)
• GB/T 11896 Water quality—Determination of chloride—Silver nitrate titration method
• GB/T 11899 Water quality—Determination of sulfate—Gravimetric method
• SH/T 0024 Determination of precipitation value of lubricating oils
• ASTM D1748-83(1993) “Determination of rust-prevention performance of metal protective agents in a humidity cabinet” (equivalent adoption)

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