SH/T 0232-1992 Liquefied petroleum gas copper strip corrosion test method

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Card type: Test method

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

• Standard number: SH/T 0232—92 (confirmed in 2004)
• Chinese name: Liquefied petroleum gas copper strip corrosion test method
• English name: not provided in the available source
• Replacement relationship: replaces SY 2083—85
• Adoption relationship: the original text states "this standard equivalently does not use international standard ISO 6251:1982 'Liquefied petroleum gas copper strip corrosion test method'"; "equivalently does not use" is suspected to be a source-text extraction error for "equivalently adopts", requires confirmation against the source standard (source-text extraction)
• Technical committee: technical committee of the Research Institute of Petroleum Processing
• Drafting organization: Maoming Petrochemical Company
• Main drafter: Zhuang Xinming
• Approval/implementation: approved by China Petrochemical Corporation 1992-05-20, implemented on 1992-05-20

2. Scope of application and non-applicability

• This standard specifies the method for the corrosion of a copper strip by a test sample.
• This standard applies to liquefied petroleum gas.
• Non-applicable scope: not provided in the available source.

3. Method principle

A polished copper strip is completely immersed in a cylinder sample containing 100 mL saturated with water and having a suitable working pressure, and placed at a temperature of 40 ℃ for 1 h. At the end of the period, the copper strip is removed, compared with the copper strip corrosion standard color plate, and rated according to the table in Appendix A.

4. Reagents and materials (purity / preparation)

• 3.2.1 Washing solvent: standard isooctane, or any volatile, sulfur-free hydrocarbon solvent that does not discolor the copper strip; analytical grade petroleum ether of 90~120 ℃ may also be used. Note: in case of dispute, standard isooctane should be used.
• 3.2.2 Copper strip: length 75 mm, width 12.5 mm, thickness 1.5~3.0 mm, made of surface-smooth hardened, cold-rolled electrolytic copper with purity of 99.9% or above. Drill a hole of diameter about 3.0 mm at 3.0 mm from the center of the end of the copper strip (the original text "diameter fire3.0mm" is suspected to be "diameter about3.0mm", requires confirmation against the source standard (source-text extraction)).
• 3.2.3 Polishing materials: 65 μm (240 grit) silicon carbide or aluminum oxide (corundum) sandpaper or emery cloth, and 105 μm (150 mesh) silicon carbide or aluminum oxide (corundum) abrasive grains, as well as medicinal absorbent cotton.
• 3.2.4 Ashless filter paper.
• Distilled water: see 6.1 (amount used about 1 mL); purity specification not provided in the available source.

5. Apparatus and equipment

• 3.1.1 Copper strip corrosion test cylinder (see figure): made of stainless steel, capacity about 160 mL. The complete assembly should withstand a static pressure test of about 7.0 MPa (70 kgf/cm²), and when tested with gas at a pressure of about 3.5 MPa (35 kgf/cm²), there should be no leakage.
• 3.1.2 Constant-temperature water bath: should be able to maintain 40 ℃±0.5 ℃, equipped with a suitable rack to keep the cylinder vertical; the water bath must be deep enough to completely immerse the cylinder and valve during the test.
• 3.1.3 Mercury thermometer: total immersion, 0~50 ℃, graduation value 0.1 ℃ (the original text "0.14" is suspected to be "0.1℃", requires confirmation against the source standard (source-text extraction)).
• 3.1.4 Chrome-plated tweezers.
• 3.1.5 Copper strip polishing clamp: firmly holds the copper strip during polishing without damaging the edges. Any suitable type may be used as long as it can clamp the copper strip and allow the polished surface to be supported on the surface of the clamp.
• Cylinder figure annotations: material is steel and stainless steel inside the needle valve; needle valve A of 1—6 mm; 2— longitudinal rubber O-shaped sealing ring; 3— copper strip; needle valve B of 4—6 mm (the original annotation has source-text extraction noise, requires confirmation against the source standard (source-text extraction)).

6. Recommended operating conditions

• Test temperature: 40 ℃±0.5 ℃ (6.6)
• Test time: 1 h±5 min (6.6)
• Sample amount: 100 mL (method summary)
• Water saturation: the sample has been saturated with water (method summary); first add about 1 mL distilled water into the cylinder to wet the cylinder wall (6.1)
• Copper strip position: the bottom edge of the copper strip is at least 6 mm from the bottom of the cylinder (6.2)
• Observation angle: observe and compare in the direction of light reflection at about 45° angle (6.8)

7. Sampling and sample preparation

• Sampling: no independent sampling clause is provided in the available source; the sample is introduced into the test cylinder from the sample source through a connecting hose (6.3).
• Test piece preparation (Chapter 5):
  • 5.1 Surface preparation: first use silicon carbide or aluminum oxide (corundum) sandpaper (or emery cloth) to remove all defects on all six faces of the copper strip, finally use 65 μm (240 grit) silicon carbide or aluminum oxide (corundum) sandpaper or emery cloth to remove all traces left by other grades of sandpaper previously used; immerse this copper strip in washing solvent for direct removal for final polishing or storage for later use.
  • Note: a practical manual polishing method is to place a sheet of sandpaper or emery cloth on a flat surface, wet it with washing solvent and make a rotating motion, rubbing the copper strip against the sandpaper, using ashless filter paper to prevent fingers from contacting the copper strip, or use dry sandpaper or emery cloth of suitable grit driven by an electric motor to machine the copper strip.
  • 5.2 Final polishing: use tweezers to remove the copper strip from the washing solvent, protect and hold it in the fingers with ashless filter paper, wet absorbent cotton with a few drops of washing solvent, pick up 105 μm silicon carbide or aluminum oxide (corundum) abrasive grains from a clean glass plate, first polish both ends, then polish the sides, then rub vigorously with fresh absorbent cotton. Next clamp the copper strip in the clamp, and use absorbent cotton to pick up 105 μm abrasive grains to polish all major surfaces, then use fresh absorbent cotton to vigorously wipe off all metal powder from the copper strip until it remains clean when wiped with a fresh absorbent cotton. During final polishing, rubbing must be along the direction of the long axis centerline of the copper strip. Before reversing the polishing direction, the stroke must exceed the end of the copper strip. During the polishing process, direct contact of fingers with the copper strip is strictly prohibited.

8. Analysis procedure

Note: throughout the entire test process, discharged gas or liquid must be discharged through a safety system.

• 6.1 Open the bottom valve B of the test cylinder, inject about 1 mL distilled water into the clean test cylinder, and rotate it to wet its wall, allowing residual liquid to drain from valve B.
• 6.2 Use tweezers to hold the freshly polished copper strip, immediately hang it on the hook of the cylinder, and place it into the cylinder (the cylinder remains vertical). During assembly, ensure that the bottom edge of the copper strip is at least 6 mm from the bottom of the cylinder. After the apparatus is assembled, close valve A and valve B.
• 6.3 Keep the test cylinder in a vertical position so that the copper strip is not wetted by water, and use a connecting hose and fittings flushed with the sample to tightly connect the sample source and valve A of the test cylinder. First open the valve on the sample source, then open valve A on the cylinder, allowing some sample to enter the cylinder.
• 6.4 Close valve A, without disconnecting the test cylinder from the sample source. Invert the test cylinder and open valve B to remove air from the test cylinder, close valve B. Then turn the test cylinder back to the vertical position, open valve B to drain all residual liquid. In the vertical position, immediately close valve B, open valve A to fill the test cylinder with sample. When the test cylinder is full, close valve A of the sample source, and disconnect the connecting hose.
• 6.5 Immediately after disconnecting the connecting hose, while the cylinder is in the upright position, slightly open valve A so that liquid above the end of the dip tube can be removed from the test cylinder. When gas first appears from valve A, close valve A.
• 6.6 Immediately immerse the cylinder in a constant-temperature water bath at 40 ℃±0.5 ℃, and let the cylinder remain in the water bath for 1 h±5 min.
• 6.7 At the end of the test, remove the cylinder from the water bath, place the cylinder in an upright position, open valve B, and discharge the liquid and most of the gas.
• 6.8 When only slight pressure remains in the cylinder, immediately disassemble the apparatus, and immediately compare the copper strip that has been exposed to liquefied petroleum gas with the corrosion standard color plate. During comparison, the test strip and the standard color plate should be observed in the direction of light reflection at about 45° angle.
• 6.9 When inspecting and comparing the test strip, if the test strip is placed in a flat test tube plugged with absorbent cotton, scratches and contamination of the test strip can be avoided.

9. Qualitative and quantitative determination and calculation formulas

• 7.1 According to how the test strip corresponds to the standard color plate, the corrosion degree of the sample may be reported as grade 1, 2, 3, or 4 as described in Appendix A.
• 7.1.1 When the appearance of a test strip is clearly between two adjacent standard color plates, its corrosion grade should be determined according to the more severely discolored standard color plate. If a test strip appears to have a deeper orange color than the grade 1 standard color plate, it is still considered to belong to grade 1; but if red is observed, the strip should be judged as grade 2.
• 7.1.2 A purple-red strip of grade 2 may be mistaken for grade 3, in which the brass-colored strip is completely covered by magenta. To distinguish them, immerse the test strip in washing solvent; the former will show dark orange, while the latter will remain unchanged.
• 7.1.3 To distinguish the multicolored strips of grade 2 and grade 3, place the test strip in a test tube of 20 mm×150 mm, lay the test tube horizontally on a heating plate, and heat at 315–370 ℃ for 4–6 min. Use another test tube with a high-temperature distillation thermometer to observe the temperature and adjust the temperature. If the test strip belongs to grade 2, it first appears silver and then gold. If it is grade 3, it will show obvious black like grade 4 and other colors.
• 7.1.4 If fingerprints are found to have soiled the test strip, causing stains, the test should be repeated.
• 7.1.5 If along the sharp edges of the flat face of the test strip a higher grade is shown than on most of the surface of the test strip, the test must also be repeated; this situation may be caused by scratching the edges of the test strip during polishing.
• 7.1.6 If brown blemishes appear on the test strip due to the addition of distilled water, these blemishes may be ignored or the test may be repeated.
• Calculation formula: not provided in the available source (this method is color plate colorimetric rating, with no calculation formula).
• Appendix A Copper strip corrosion standard color plate grading table:
  • Newly polished copper strip: only serves as an appearance marker for the copper strip before polishing in the test; even with a completely non-corrosive sample, this appearance cannot be reproduced after the test.
  • 1 grade slight tarnish: a. pale orange, almost the same as a newly polished copper strip; b. dark orange.
  • 2 grade moderate tarnish: a. magenta; b. pale purple; c. multicolor with pale purplish blue, or silver, or both, each overlaid on magenta; d. silver; e. brass or golden yellow.
  • 3 grade deep tarnish: a. multicolor with magenta overlaid on brass; b. multicolor shown by red and green (peacock green), but without gray (original text "but without color" suspected missing character, requires confirmation against the source standard (source-text extraction)).
  • 4 grade corrosion: a. transparent black, dark gray, or brown with slight peacock green (the source adjective is unclear; its interpretation as transparent remains unverified); b. graphite black or matte black; c. glossy black or jet black.
• Appendix A Color plate storage and replacement: A1 The corrosion standard color plates are full-color reproductions, printed on aluminum plates through four color processing treatments; mounted in a plastic sleeve in metal plate form, each metal plate has instructions on the reverse side. A2 Should be protected from light to prevent fading; check the degree of fading by comparing the difference between two standard color plates, one of which is a new standard color plate carefully stored away from light; observe under scattered light, first from above, then from a 45° angle; if any sign of fading is observed, especially signs of fading at the left end of the color plate, it is recommended to discard the severely faded color plate. A3 Another method is when purchasing new color plates, place a series of 20 mm wide light-blocking strips horizontally on top of the colored portion of the color plate, then from time to time remove the light-blocking strips and check for any signs of fading at the top of the newly exposed color plate; if any fading occurs, the standard color plate should be replaced with a new one. A4 If deep scratches appear on the surface of the plastic sleeve, it is recommended to replace with a new standard color plate.

10. Precision

not provided in the available source.

11. Report

• Report the degree of corrosion of the sample according to grade 1, 2, 3 or 4 as described in Appendix A (7.1).
• Report format, report form content: not provided in the available source.

12. Reference documents

• ISO 6251:1982 "Liquefied petroleum gas copper strip corrosion test method" (equivalent adoption relationship, original wording requires confirmation against the source standard (source-text extraction))
• SY 2083—85 (replaced)
• Appendix A Copper strip corrosion standard color plate (supplementary document)

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 Q&A