JB/T 6074-1992 \u8150\u8680\u8bd5\u6837\u7684\u5236\u5907\u3001\u6e05\u6d17\u548c\u8bc4\u5b9a
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Mechanical Industry Standard of the People's Republic of China
JB/T6074-92
Preparation, Cleaning and Evaluation of Corrosion Samples
Published on May 5, 1992
Implemented on July 1, 1993 by the Ministry of Machinery and Electronics Industry of the People's Republic of China
Published
Mechanical Industry Standard of the People's Republic of China
Preparation, Cleaning and Evaluation of Corrosion Samples
1 Subject Content and Scope of Application
JB/T6074-92
This standard specifies the preparation of metal samples for corrosion tests, the removal of corrosion products and the evaluation method of corrosion losses. This standard is applicable to various corrosion tests under laboratory conditions, and can also be applied to the preparation, cleaning and evaluation of various corrosion test samples under natural environmental conditions.
2 Samples
2.1 Sampling
2.1.1 Samples can be taken directly from the product or from the same batch of raw materials used to manufacture the product. 2.1.2 This standard does not include sampling of the entire product. 2.2 Shape and size of the sample
2.2.1 The shape and size of the sample depend on the purpose of the test, the nature of the material and the container used. The sample with a large ratio of surface area to mass and a small ratio of edge area to total area should be used as much as possible. 2.2.2 The total surface area of each sample should not be less than 10cm2. Two shapes of samples are recommended, and their specifications are as follows: Plate sample: 1×b×h, cm: 5.00×2.50×(0.20~0.30) 3.00×1.50×(0.15~0.30)
Circular sample: medium×h, cm: 3.80×(0.20~0.30) 3.00×(0.20~0.30)
2.2.3
2.2.4
The shape and specifications of the samples tested in the same batch should be the same. For each test, at least 3 parallel samples should be taken. 2.3 Surface condition adjustment of the sample
2.3.1
2.3.2
The surface of the sample used in the corrosion test should simulate the surface condition of the product as much as possible. Surface condition adjustment steps of the sample
Grind with metallographic sandpaper or diamond paste to remove the burrs on the edge and surface of the sample. Degrease the sample in acetone, alcohol or hot alkaline cleaning agent. When there is an oxide film or rust on the surface of the sample, it is generally cleaned using the chemical method in Article 3.2. After the sample is thoroughly cleaned with water, it is placed in anhydrous alcohol. d. Drying. 2.4 Adjustment of the metallurgical state of the sample The metallurgical state should not be changed during the sample preparation process. If there is a change, it should be corrected by subsequent heat treatment, machining or other methods. 2.5 Measurement and weighing of the sample The measurement and weighing of the sample must be carried out after cleaning and drying. The size is accurate to 0.01cm* and the mass is accurate to 0.001g. 3 Methods for removing corrosion products after sample testing 3.1 Electrolytic cleaning method 3.1.1 After wiping off the loose corrosion products on the surface of the sample, immerse the sample in the electrolyte for electrolysis. Approved by the Ministry of Machinery and Electronics Industry on May 5, 1992, and implemented on July 1, 1993
3.1.2 Electrolyte formula and process
Sulfuric acid (H2SO
Organic corrosion inhibitor”
Distilled water
Temperature
Time
Cathode
Current density
Density 1.84)
28mL
JB/T6074-92
1000mL
75℃
3min
Graphite or lead\
Sample
20A/dm
Note: 1) Di-o-toluene thiourea or hexamethylenetetramine with a concentration of 0.5g/L can be used as a corrosion inhibitor. 2) When using lead as the anode, lead may precipitate on the sample, causing mass loss errors. If the sample is resistant to nitric acid, the lead in the sample can be removed by slightly immersing the sample in 1:1 nitric acid. Although lead deposition may cause mass loss errors, its corrosion products are easy to remove. Still used as anode material. 3.2 Chemical cleaning method
Use the solution formula and process in Table 1 according to different materials. Table 1
Metallic materials
Stainless steel
Aluminum and aluminum alloys
Copper, nickel and their alloys
Tin and tin alloys
Magnesium and magnesium alloys
Zinc and zinc alloys
Cleaning method
Solution composition
①20% sodium hydroxide, 200g/L zinc powder
Immersion 1
④Hydrochloric acid (HC1 density 1.19) 1000mL, antimony oxide (Sb:0s) 20g, tin fluoride (SnC1:) 50g③Sulfuric acid (H,SO. density 1.84) 100mL, organic corrosion inhibitor 1.5mL, steamed filling water 1000mL
Alternate immersion 9
①Nitric acid (HNO density 1.42) 100mL, steamed filling water 1000mL
②Ammonium citrate 150g, distilled water 1000mL
Immersion ①Chromic anhydride (Cr Os) 20g, phosphoric acid (H,PO, density 1.69) 50mL, distilled water 1000mL
② Nitric acid (HNO, density 1.42)
Hydrochloric acid (HC1 density 1.19) 500mL, distilled water soak
1000mL
Sodium phosphate (Na:PO.) 150g, distilled water 1000 soak
Chromic anhydride (CrO), 150gSilver chromate (Ag:CrO) 10g, steamed stuffing water 1000mL
Alternate soaking ①Acetic acid (99.5%) 10mL, distilled water 1000mL②Ammonium acetate 50g, distilled water 1000mL
Saturated ammonium acetate (CH:COONH)
Alternate soaking ①Ammonium hydroxide (NH,OH density 0.90) 150mL, distilled water 1000mL
②Chromic anhydride (Cr0:) 50g, nitric acid
Silver (Ag NO,) 10g, distilled water 1000mL treatment conditions
Temperature ℃
Boiling
Room temperature
Room temperature
Room temperature
Boiling
Boiling
Boiling
Room temperature
Boiling time min
10~60
5~10
Until clean
Until clean
10~20
1~10
Be careful
The solution must be stirred vigorously, or use
Eraser, wooden tools to scrub the sample
Organic corrosion inhibitor is hexamethylenetetramine or thiourea
Method ① in steel can also be used
If there is still a layer of film, immerse in ②
Wash for 1min
Most of the corrosion products should be removed before treatmentbzxz.net
It is best to use electrolytic cleaning method
Chromic anhydride is not allowed to contain sulfate. In the preparation, silver nitrate is dissolved and then
Added to boiling chromic acid
3.3 Mechanical cleaning method
JB/T607492
This method can be used to replace or supplement the chemical cleaning method to remove attached precipitates. A soft scraper or fiber bristle brush should be used to avoid damaging the sample matrix.
3.4 The samples cleaned by the above methods should be cleaned in running water and gently scrubbed with a brush. If necessary, they can be repeatedly cleaned and soaked. The cleaned samples are placed in anhydrous alcohol, taken out and dried, and then placed in a dry coal dryer to cool to air temperature before weighing. 4 Evaluation of corrosion damage
4.1 Calculation of corrosion rate
4.1.1 Regardless of the cleaning method used, there is a possibility of damaging the base metal, which causes errors in the corrosion rate measurement. In order to correct this, one or more cleaned and weighed samples can be used. Re-clean and re-weigh in the same way, and the corrected mass loss value is calculated according to formula (1).
W=(W,- W2)-(W,-Ws)
Where: AW-corrected mass loss value, g; W,--mass of the sample before corrosion test, g; W--mass of the sample after corrosion test and removal of corrosion products·g; W,--mass of the sample after re-cleaning, g
For more accurate correction methods, see Appendix A (Supplement). 4.1.2 Calculate the average corrosion rate or the corrected corrosion rate according to formula (2) and (3). K(W-W)
R=K(W.-2Wa+W.)
Where: \-corrosion rate;
R-corrected corrosion rate;
K constant (see 4.1.3);
W, mass of the sample before the corrosion test, g, accurate to 0.001g; Wr
-mass of the sample after removing the corrosion products, g, accurate to 0.001g; W,-mass of the sample after re-cleaning, g, accurate to 0.001g; S--surface area of the sample, cm2. Accurate to 0.01cm2; T corrosion test time.h. Accurate to 0.01h; D density, g/cm
4.1.3 When T, S, W, and D are in the units specified in 4.1.2, the corrosion rate can be expressed in multiple units using the following appropriate K values. Corrosion rate unit
mm/a (millimeter/year)
(m/a (micrometer/year)
pm/s (picometer/second)
g/(mh) gram/(meter hour)
mg/(dmd) [milligram/(decimeter2.day)
μg/(ms) microgram/(meter2second)]
K value
8.76×10
8.76×107
2.78×106
1.00×10*×D
2.40×10°×D
2.73×10×D
· (3)
4.1.4 In 4.1.3, when calculating the corrosion rate in the last three units, there is no need to find the material density D value. The density of the constant K is exactly the same as the D low pin in the corrosion rate formula.
4.1.5 If necessary, these constants can also be used to convert the corrosion rate from one unit to another. In order to convert a corrosion rate in one unit to a corrosion rate in another unit, you can multiply it by K,/K. For example: 3
JB/T6074—92
2.78×106
1mm/a=1x-
8. 76×104
pm/s
When pitting corrosion exists, the corrosion rate calculated from the mass loss will be in error, and the corresponding pitting corrosion assessment method can be selected. 4.2
4.3 Other methods for assessing corrosion damage
4.3.1 Appearance Assess the change in appearance through rust, discoloration or oxidation. Mechanical properties If the cross-sectional area of the specimen (measured value before the corrosion test) is reduced due to extensive corrosion, it will cause a decrease in tensile strength. 4.3.2
Local corrosion (such as cracking) can also cause a decrease in tensile strength and elongation. 4.3.3 Electrical properties Cracking and pitting can cause Apparent conductivity decreases. Metallographic examination Separation, peeling, cracking or intergranular corrosion can be evaluated by preparing metallographic specimens of the surface. 4.3.4
5 Report
The report should include the sample composition, size, metallurgical conditions, surface preparation and cleaning methods of corrosion products after the test, as well as the evaluation results of corrosion damage.
JB/T607492
Appendix A
Method for accurate determination of mass loss
(Supplement)
A1 Repeatedly clean several times, weigh after each cleaning and draw a curve of mass loss and total cleaning time or number of cleaning times. See Figure A1. Curve The vertical bar of the inflection point is the mass loss caused by the removal of corrosion products alone. This method is particularly suitable for electrolytic cleaning. Mass of corrosion products removed
Removed substrate
Removed corrosion products
Cleaning time
Figure A1
Additional notes:
Relationship between mass loss and cleaning time during cleaning This standard was proposed and coordinated by the Wuhan Materials Protection Research Institute of the Ministry of Machinery and Electronics Industry. This standard was drafted by the Wuhan Materials Protection Research Institute. The main drafters of this standard were Yu Hongying and Fang Yisan. China
Mechanical Industry Standard
Preparation, Cleaning and Evaluation of Corrosion Test Specimens
JB/T 6074-92
Published by the Mechanical Standardization Research Institute of the Ministry of Machinery and Electronics Industry and printed by the Mechanical Standardization Research Institute of the Ministry of Machinery and Electronics Industry (Box 8144, Beijing 100081)
Copyright reserved
No reproduction allowed
Format 880×12301/16
Printing sheet 1/2
Word count 10,000
First edition September 1992
First printing September 1992
Print run 00,001-700
Price 1.20 yuan
No. 0637
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