General specification for multifunctional solution of steel and iron surface treatment
Some standard content:
National Standard of the People's Republic of China
General Specification for Multifunctional Surface Treatment Liquids for Sleel and Iron Surface Treatment1 Subject Content and Scope of Application
GB/T12612—90
This standard specifies the classification, technical requirements, inspection methods and inspection rules for multifunctional surface treatment liquids for steel (hereinafter referred to as treatment liquids) which are mainly composed of phosphoric acid and phosphoric acid precipitates and other additives. This standard applies to the pre-production of comprehensive surface treatment of steel workpieces before painting in the factory as working liquids: it also applies to products with the same characteristics. When leaving the factory, the solid and liquid components are packaged or concentrated separately and then prepared into a working liquid when used. 2 Reference Standards
Method for Preparation of Standard Solutions of Chemical Reagents
(iB1720 Determination of Adhesion of Paint Films
GB1771 Determination of Salt Spray Resistance of Paint Films
GB6163 Review of Thickness Measurement Methods for Metal and Other Inorganic Covering Layers GB 6807
3 Terminology
3.1 Function
Technical conditions for phosphating treatment of steel workpieces before painting: degreasing, descaling, phosphating, passivation or more than one function: 3.2-L working liquid
Liquid diameter in actual use,
4 Classification and marking symbols
4.1 The treatment liquid is divided into the following according to its function:
Descaling, rust removal, phosphating, passivation treatment liquid with four functions, marking symbol 1; rust removal, magnetization, degreasing (or passivation) treatment liquid with one function. Marking symbol 3: Rust removal dual-function treatment liquid. Marking symbol less 2. 4.2 Treatment is divided into the following according to rust removal ability:
Treatment liquid that can remove heavy rust and general oxide scale, marked with symbol A; treatment liquid that can remove floating rust, light rust and medium rust, marked with symbol A2. 4.3 Treatment liquid is divided into the following according to use temperature:
Normal temperature (15~15℃), marked with symbol B: Medium temperature (45~-65()), marked with symbol B2. 4.4 The current liquid is divided into the following according to the factory status:
State Technical Supervision Bureau "99012.18 approved 1991-12-01 For liquid, mark L; for concentrated liquid, mark M, where x is the concentration multiple; for solid and liquid components, mark N. 4.5 Product marking GB/T12612 4.5.1 Product marking consists of product name, product category marking symbol and standard number, as follows: xx Function number Single use number Rare addition capacity Product name 4.5.2 Product name (including model) is determined by the manufacturer 4.5.3 Marking example:
One number
Using temperature
Four functions to remove heavy rust and scale, easy to use at room temperature, working state is excellent! The treatment liquid is marked as: saw iron treatment carboxylic acid AIRIL (iUT [2612
5 Technical requirements
5.1 Appearance and sensory requirements
The appearance of the working liquid should be a homogeneous liquid, without obvious sedimentation and no strong irritating odor. 5. 2 Physical and chemical properties
GB/T 12612
Output state
The main technical indicators of the physical and chemical properties of the treatment liquid are: call value, total gel point, free acid point and density. The main technical indicators of the service treatment liquid should be clearly specified, and the products shipped from the factory should meet the requirements of the tender. 5. 3 Performance in use
5. 3. 1 Rust removal capability
For the two types of products classified by rust removal capability (A1, A2) specified in Article 4.2, the treated test piece H should be free of rust spots or agreed upon by both parties. The original rust condition is evaluated in Appendix C (reference). 5.3.2 Oil removal capability
After the treated test piece, the water film should be continuous in daylight. 5.3.3 Apparent quality of phosphate film
5.3.3.1The surface of the treated test piece should form a uniform charcoal, black or rainbow phosphate film: 5.3.3.2When the treated test piece has the following conditions or one of them, it is an allowable defect: slight water marks;
b, the rusted area is inconsistent with the overall color
5.3.3.3When the treated test piece has the following conditions, it is an allowable defect: a.
There is residual oil film on the surface;
The rust has not been completely removed, and new water rust appears!
r: The surface shows a group of:
5.3.4 Unit weight of phosphate film
The unit weight of the phosphate film of the treated test piece shall comply with the specifications of the sub-light grade or light grade shown in the table of EN 6807, that is, the unit weight of the sub-light grade film is 0.2~1.0 island/m, and the unit weight of the light grade film is 1.1-~4.5/m*5.3.5 Corrosion resistance of phosphate film
5.3.5.1 Anti-rust period
GB/T 12612-90
The test piece after treatment and drying shall be stored at room temperature with a relative humidity of less than 70% and no corrosive gas. The anti-rust period shall not be less than 5d.
5.3.5.2 Immersion test
Inspect according to the method specified in 6.3.6.1. After 1h, no rust shall appear on the steel surface (except for edges and sides). 5.3.5.3 Spot test
It can be used as a quick test of the quality of the phosphate film between processes. The color change time shall be agreed upon by the supply and demand parties. 5.3.6 Paint film matching performance
5. 3. 6. 1 Paint film corrosion resistance
Test according to the method specified in 6.3.7. After 8h salt spray resistance test, except for the 0.5mm on any side of the scratched part, the paint film should not have blistering, shedding, rust and other phenomena.
5. 3.6.2 Paint film adhesion
Test according to the method specified in CB1720. The adhesion should not be lower than level 2. 5. 4 Storage performance
The product is valid for one year from the date of production under the condition of good packaging and storage at an ambient temperature of -30 to +40℃. If the storage period exceeds the storage period, it shall be tested item by item according to the provisions of this standard. Qualified products can still be used. 6 Inspection methods
6.1 Appearance inspection of treatment
Under natural light or mixed lighting, visually inspect for precipitation or floccules. 6.2 Physical and chemical properties of treatment solution
6.2.1 pH value
Measure with pH test paper or pH i1.
6.2.2 Determination of free acidity and total acidity
Perform according to Appendix A (Supplementary)
6.2.3 Density
Measure with a hydrometer at 20±1℃.
6.3 Method for determination of performance of treatment solution
6.3.1 Preparation of test pieces
6. 3.1.1 Rust test pieces
Select cold-rolled steel test pieces of 50mm×120mm×1mm with different rust conditions. The evaluation of the rust condition of the test pieces is shown in Appendix C. 6.3.1.2 Oil-coated rust test piece
Use the rust test piece specified in 6.3.1.1, and dip it in 30* engine oil (the amount of oil at air temperature is about 1.2mg/cm°). 6.3.1,3 Oil-coated test piece
Use a 70mm×150mm×1mm cold-rolled steel test piece, treat it according to the method in 6.3.2, and spray it with a layer of A04-9 white aminoacetylene paint with a thickness of 25~～35μm, and dry it at room temperature for 30min: then keep it in a blast drying oven (102~107℃) for 2b, and then place it at room temperature for one day for testing.
6-3.2 Test piece treatment method
6.3.2.1 Treatment method with two or four functional treatment liquids Place the oiled rust test piece prepared in accordance with 6.3.1.2 into a 1000mL beaker containing the working liquid, and wash it for 10~~20 minutes according to different treatment temperature requirements, including 3~~6 minutes of swing washing, and then take it out and dry it naturally. 6.3.2.2 Treatment method with two or one functional treatment liquids 90
GB/T 12612
For the test piece prepared in accordance with the requirements of 6.3.1.1, the treatment steps are the same as those specified in 6.3.2.1. 6.3.3 Oil removal ability test method
The test piece treated in accordance with 6.3.2.1 should be immediately rinsed with water and the continuity of the water film should be visually inspected under natural light or mixed lighting conditions. 6.3.4 Rust removal ability test method
After the test piece is treated, visually check whether there are any residual rust spots on the surface. 6.3.5 Unit weight of phosphate film
After the test piece is treated by the method in 6.3.2, the unit weight of the phosphate film shall be determined according to Appendix B (Supplement). 6.3.6 Corrosion resistance test method of phosphate film
6.3.1 Immersion test
Immerse the treated test piece in 3% sodium fluoride solution (20±2°C), take it out after 1 hour, wash and blow dry. Visually check whether there is any rust on the surface of the test piece.
6.3.6.2 Drop test
Continue with Appendix D of GH 6807.
6.3.7 Corrosion resistance test of paint film
Use a No. 18 sewing machine needle to scratch the paint film into a cross diagonal line of 120 mm in length on the paint test piece prepared in accordance with 6.3.1.3, and the scratch should be deep to the test piece substrate. Take three samples, with the scratched side facing up, and keep them in the disk fog test box, and test them according to the conditions specified in GB1771. When checking, rinse the surface of the test piece with tap water to remove the salt deposits, and after quick drying with cold air, visually check the surface of the test piece. 7 Inspection rules
7.1 Factory inspection
7.1.1 The factory products shall be identified and inspected by the quality inspection department, and the bowl shall meet the technical index requirements and be accompanied by a product quality certificate. 7.1.2 Factory inspection items include: appearance, physical and chemical properties and performance requirements of 5.3.3, 5.3.5, and 5.3.6. 7.1.3 The additional inspection items agreed upon by both parties should be included in the factory inspection. 7.2 Type inspection
A comprehensive inspection should be carried out in accordance with the technical requirements specified in this standard and product standards. 7.2.1
7.2.2 Type inspection should generally be carried out when one of the following situations occurs:
When trial production and finalization of new products are carried out;
When the process and formula have been greatly changed, which may affect the product performance; When the national, provincial, and municipal quality supervision agencies have put forward the requirement for type inspection. 7.3 Sampling method
Samples should be taken from 5% of the containers of each batch of production, with a total sampling volume of 500mL. Put them in a clean narrow-necked bottle and wait for inspection. If the inspection fails, double sampling should be carried out: If the inspection fails again, it cannot be shipped out of the factory. 8 Marking, packaging, transportation, storage
8.1 Marking
Products must be marked with the manufacturer's name, product mark, product model and manufacturing date or production batch number. 8.2 Packaging
The treatment liquid should be packaged in plastic or other acid-resistant containers. 8.3 Storage and transportation
This product cannot be transported together with food, daily necessities and alkaline substances. GB/T 12612 90
Appendix A
Determination of free acidity and total acidity
(Supplement)
This method uses acid-base titration. Take 10mL of the sample and titrate it with 0.1mol/l sodium hydroxide standard solution. The number of milliliters consumed is indicated by points.
Al reagent
Sodium hydroxide: 1mol/T. standard solution (prepared and calibrated according to GB601)) phenolic indicator% ethanol solution:
Methyl orange indicator: 0.1% aqueous solution,
Bromophenol blue indicator 1 dissolved in 000mL20% ethanol. A2 Test method
A2.1 Determination of free acidity
Use a pipette to draw 10ml of the test solution into a 250mL conical flask, add 50mL of distilled water, and 2~3 drops of methyl orange indicator (or bromophenol blue indicator). Titrate with sodium hydroxide standard solution until the solution turns orange (or with bromophenol blue indicator solution, the solution turns from yellow to blue-purple), which is the end point. Record the number of milliliters of sodium hydroxide standard solution consumed. AA2.2 Measurement of total acidity
Pipette 10mL of test solution into a 250mL conical flask 1, add 50㎡L of distilled water: add 2~3 drops of phenol indicator solution: titrate with sodium hydroxide standard solution until the solution turns pink, which is the end point. Record the number of milliliters of sodium hydroxide standard solution consumed B. A3 Calculation method
The acidity points are calculated according to the following formula:
Free acidity (points)
Total acidity (points)
Where: A, B
The number of liters of sodium hydroxide standard solution consumed during titration, mL; the actual concentration of ammonia oxidation standard solution + mal/l; - the number of liters of the group, mL.
10 Ac:
Appendix B
Method for determining the unit mass of phosphate film
(Supplement)
This method is applicable to the measurement of the mass of the film layer per unit area of the phosphate film formed on the surface of steel. Instruments
Analytical balance: Sensitivity is 0.1mg:
Heating equipment: used to determine the concentration of the film stripping solution, B2 sample
The total surface area of the sample with a unit mass of less than 1 g/m2 should not be less than 400 cm2; the total surface area of the sample with a unit mass of 1~-10 g/m2 should not be less than 200 cm2
B3 Film stripping
GB/1 12612- 90
Take 50g of chromium trioxide (Cr0) and prepare 1000ml solution with distilled water. B4 Test method
Weigh the treated and dried test piece with an analytical balance with a sensitivity of 0.1m (m). Then immerse the test piece in the film stripping solution, maintain it at 75±5℃ for a short time, soak it for 15 minutes, rinse it with clean water immediately, and then wash it with distilled water. Weigh it after drying until the constant weight (mz). B5 Calculation
The mass of the phosphate coating per unit area is calculated according to the following formula, ×10
In the formula, a is the mass of the phosphate coating per unit area, B/m; m, — the mass of the sample after phosphating, mg:
·The mass of the sample after film removal, work name:
A-the total surface area of the sample.cm.
Take the average value of a parallel measurement sample. Appendix C
Evaluation of the rust condition of steel surface
(reference)
This method is applicable to the evaluation of the rust condition of general workpieces. The corrosion depth can be measured according to the profilometer method in GB6163+1.2.3. The corrosion degree can be measured by the corrosion assessment plate method. The assessment plate is made of a 50mm×50mm×2mm colorless transparent plate with a 40mm×40mm square frame in the middle. There are 100 4mmX4mm square grids engraved in the frame. When measuring, the corrosion assessment plate and the tested test piece are re-selected, and the number of squares with corrosion in the 100 squares is visually checked. The percentage is expressed as the degree of corrosion. C3 Evaluation of corrosion status
The corrosion depth is mainly evaluated, supplemented by the degree of corrosion and surface condition, and a comprehensive evaluation is performed. As shown in Table C1. Table CI
Rust condition
Rust depth,
Rust degree, %
Surface state
Floating rust, light rust
Yellow or light red
≥30-80
Surface rough, reddish brown or light brown
51~100
To dark brown, rust layer raised in flakes
Additional remarks:
GB/T12612
This standard was proposed by the Ministry of Aerospace Industry of the People's Republic of China. 90
This standard was put forward by the National Technical Committee for Standardization of Metallic and Non-metallic Coverings. This standard was drafted by the 31st Institute of the Third Academy of the Ministry of Aerospace Industry. The main drafters of this standard are Hu Meihua, Pei Erquan, and Zhang Jiahua.3 Storage and transportation
This product cannot be transported together with food, daily necessities and alkaline substances. GB/T 12612 90
Appendix A
Determination of free acidity and total acidity
(Supplement)
This method uses acid-base titration. Take 10mL of the sample and titrate it with 0.1mol/l. sodium hydroxide standard solution. The number of milliliters consumed is indicated by points.
Al reagent
Sodium hydroxide: 1mol/T. standard solution (prepared and calibrated according to GB601)) Phenolic indicator % ethanol solution:
Methyl orange indicator: 0.1% aqueous solution,
Bromolybdenum blue indicator 1 is dissolved in 000mL 20% ethanol. A2 Test method
A2.1 Determination of free acidity
Use a pipette to draw 10ml of test solution into a 250mL conical flask, add 50mL of distilled water, and 2~3 drops of phenol indicator (or bromophenol blue indicator). Titrate with sodium hydroxide standard solution until the solution turns orange (or changes from yellow to blue-purple when titrated with bromophenol blue indicator), which is the end point. Record the number of milliliters of sodium hydroxide standard solution consumed. A2.2 Measurement of total acidity
Use a pipette to draw 10mL of test solution into a 250mL conical flask1, add 50mL of distilled water: add 2~3 drops of phenol indicator: titrate with sodium hydroxide standard solution until the solution turns pink, which is the end point. Record the number of milliliters of sodium hydroxide standard solution consumed. B. A3 Calculation method
The acidity points are calculated according to the following formula:
Free acidity (points)
Total acidity (points)
Where: A, B
The number of liters of sodium hydroxide standard solution consumed during titration, mL; the actual concentration of ammonia oxidation standard solution + mal/l; - the number of liters of the group, mL.
10 Ac:
Appendix B
Method for determining the unit mass of phosphate film
(Supplement)
This method is applicable to the measurement of the mass of the film layer per unit area of the phosphate film formed on the surface of steel. Instruments
Analytical balance: Sensitivity is 0.1mg:
Heating equipment: used to determine the concentration of the film stripping solution, B2 sample
The total surface area of the sample with a unit mass of less than 1 g/m2 should not be less than 400 cm2; the total surface area of the sample with a unit mass of 1~-10 g/m2 should not be less than 200 cm2
B3 Film stripping
GB/1 12612- 90
Take 50g of chromium trioxide (Cr0) and prepare 1000ml solution with distilled water. B4 Test method
Weigh the treated and dried test piece with an analytical balance with a sensitivity of 0.1m (m). Then immerse the test piece in the film stripping solution, maintain it at 75±5℃ for a short time, soak it for 15 minutes, rinse it with clean water immediately, and then wash it with distilled water. Weigh it after drying until the constant weight (mz). B5 Calculation
The mass of the phosphate coating per unit area is calculated according to the following formula, ×10
In the formula, a is the mass of the phosphate coating per unit area, B/m; m, — the mass of the sample after phosphating, mg:
·The mass of the sample after film removal, work name:
A-the total surface area of the sample.cm.
Take the average value of a parallel measurement sample. Appendix C
Evaluation of the rust condition of steel surface
(reference)
This method is applicable to the evaluation of the rust condition of general workpieces. The corrosion depth can be measured according to the profilometer method in GB6163+1.2.3. The corrosion degree can be measured by the corrosion assessment plate method. The assessment plate is made of a 50mm×50mm×2mm colorless transparent plate with a 40mm×40mm square frame in the middle. There are 100 4mmX4mm square grids engraved in the frame. When measuring, the corrosion assessment plate and the tested test piece are re-selected, and the number of squares with corrosion in the 100 squares is visually checked. The percentage is expressed as the degree of corrosion. C3 Evaluation of corrosion status
The corrosion depth is mainly evaluated, supplemented by the degree of corrosion and surface condition, and a comprehensive evaluation is performed. As shown in Table C1. Table CI
Rust condition
Rust depth,
Rust degree, %
Surface state
Floating rust, light rust
Yellow or light red
≥30-80
Surface rough, reddish brown or light brown
51~100
To dark brown, rust layer raised in flakes
Additional remarks:
GB/T12612
This standard was proposed by the Ministry of Aerospace Industry of the People's Republic of China. 90
This standard was put forward by the National Technical Committee for Standardization of Metallic and Non-metallic Coverings. This standard was drafted by the 31st Institute of the Third Academy of the Ministry of Aerospace Industry. The main drafters of this standard are Hu Meihua, Pei Erquan, and Zhang Jiahua.3 Storage and transportation
This product cannot be transported together with food, daily necessities and alkaline substances. GB/T 12612 90
Appendix A
Determination of free acidity and total acidity
(Supplement)
This method uses acid-base titration. Take 10mL of the sample and titrate it with 0.1mol/l. sodium hydroxide standard solution. The number of milliliters consumed is indicated by points.
Al reagent
Sodium hydroxide: 1mol/T. standard solution (prepared and calibrated according to GB601)) Phenolic indicator % ethanol solution:
Methyl orange indicator: 0.1% aqueous solution,
Bromolybdenum blue indicator 1 is dissolved in 000mL 20% ethanol. A2 Test method
A2.1 Determination of free acidity
Use a pipette to draw 10ml of test solution into a 250mL conical flask, add 50mL of distilled water, and 2~3 drops of phenol indicator (or bromophenol blue indicator). Titrate with sodium hydroxide standard solution until the solution turns orange (or changes from yellow to blue-purple when titrated with bromophenol blue indicator), which is the end point. Record the number of milliliters of sodium hydroxide standard solution consumed. A2.2 Measurement of total acidity
Use a pipette to draw 10mL of test solution into a 250mL conical flask1, add 50mL of distilled water: add 2~3 drops of phenol indicator: titrate with sodium hydroxide standard solution until the solution turns pink, which is the end point. Record the number of milliliters of sodium hydroxide standard solution consumed. B. A3 Calculation method
The acidity points are calculated according to the following formula:
Free acidity (points)
Total acidity (points)
Where: A, B
The number of liters of sodium hydroxide standard solution consumed during titration, mL; the actual concentration of ammonia oxidation standard solution + mal/l; - the number of liters of the group, mL.
10 Ac:
Appendix B
Method for determining the unit mass of phosphate film
(Supplement)
This method is applicable to the measurement of the mass of the film layer per unit area of the phosphate film formed on the surface of steel. Instruments
Analytical balance: Sensitivity is 0.1mg:
Heating equipment: used to determine the concentration of the film stripping solution, B2 sample
The total surface area of the sample with a unit mass of less than 1 g/m2 should not be less than 400 cm2; the total surface area of the sample with a unit mass of 1~-10 g/m2 should not be less than 200 cm2
B3 Film stripping
GB/1 12612- 90
Take 50g of chromium trioxide (Cr0) and prepare 1000ml solution with distilled water. B4 Test method
Weigh the treated and dried test piece with an analytical balance with a sensitivity of 0.1m (m). Then immerse the test piece in the film stripping solution, maintain it at 75±5℃ for a short time, soak it for 15 minutes, rinse it with clean water immediately, and then wash it with distilled water. Weigh it after drying until the constant weight (mz). B5 Calculation
The mass of the phosphate coating per unit area is calculated according to the following formula, ×10
In the formula, a is the mass of the phosphate coating per unit area, B/m; m, — the mass of the sample after phosphating, mg:
·The mass of the sample after film removal, work name:
A-the total surface area of the sample.cm.
Take the average value of a parallel measurement sample. Appendix C
Evaluation of the rust condition of steel surface
(reference)
This method is applicable to the evaluation of the rust condition of general workpieces. The corrosion depth can be measured according to the profilometer method in GB6163+1.2.3. The corrosion degree can be measured by the corrosion assessment plate method. The assessment plate is made of a 50mm×50mm×2mm colorless transparent plate with a 40mm×40mm square frame in the middle. There are 100 4mmX4mm square grids engraved in the frame. When measuring, the corrosion assessment plate and the tested test piece are re-selected, and the number of squares with corrosion in the 100 squares is visually checked. The percentage is expressed as the degree of corrosion. C3 Evaluation of corrosion status
The corrosion depth is mainly evaluated, supplemented by the degree of corrosion and surface condition, and a comprehensive evaluation is performed. As shown in Table C1. Table CI
Rust condition
Rust depth,
Rust degree, %
Surface state
Floating rust, light rust
Yellow or light red
≥30-80
Surface rough, reddish brown or light brown
51~100Www.bzxZ.net
To dark brown, rust layer raised in flakes
Additional remarks:
GB/T12612
This standard was proposed by the Ministry of Aerospace Industry of the People's Republic of China. 90
This standard was put forward by the National Technical Committee for Standardization of Metallic and Non-metallic Coverings. This standard was drafted by the 31st Institute of the Third Academy of the Ministry of Aerospace Industry. The main drafters of this standard are Hu Meihua, Pei Erquan, and Zhang Jiahua.3. Determination by the profilometer method. The corrosion degree is determined by the rust assessment plate method. The assessment plate is made of a 50mm×50mm×2mm colorless transparent plate with a 40mm×40mm square frame in the middle. There are 100 4mmX4mm square grids engraved in the frame. When measuring, the rust assessment plate and the test piece to be measured are re-selected, and the number of rusted squares in the 100 squares is visually inspected. The percentage is expressed as the degree of corrosion. C3 Evaluation of rust condition
The evaluation is mainly based on the depth of corrosion, supplemented by the degree of corrosion and surface condition, and a comprehensive evaluation is made. As shown in Table C1. Table CI
Rust condition
Rust depth,
Rust degree, %
Surface state
Floating rust, light rust
Yellow or light red
≥30-80
Surface rough, reddish brown or light brown
51~100
To dark brown, rust layer raised in flakes
Additional remarks:
GB/T12612
This standard was proposed by the Ministry of Aerospace Industry of the People's Republic of China. 90
This standard was put forward by the National Technical Committee for Standardization of Metallic and Non-metallic Coverings. This standard was drafted by the 31st Institute of the Third Academy of the Ministry of Aerospace Industry. The main drafters of this standard are Hu Meihua, Pei Erquan, and Zhang Jiahua.3. Determination by the profilometer method. The corrosion degree is determined by the rust assessment plate method. The assessment plate is made of a 50mm×50mm×2mm colorless transparent plate with a 40mm×40mm square frame in the middle. There are 100 4mmX4mm square grids engraved in the frame. When measuring, the rust assessment plate and the test piece to be measured are re-selected, and the number of rusted squares in the 100 squares is visually inspected. The percentage is expressed as the degree of corrosion. C3 Evaluation of rust condition
The evaluation is mainly based on the depth of corrosion, supplemented by the degree of corrosion and surface condition, and a comprehensive evaluation is made. As shown in Table C1. Table CI
Rust condition
Rust depth,
Rust degree, %
Surface state
Floating rust, light rust
Yellow or light red
≥30-80
Surface rough, reddish brown or light brown
51~100
To dark brown, rust layer raised in flakes
Additional remarks:
GB/T12612
This standard was proposed by the Ministry of Aerospace Industry of the People's Republic of China. 90
This standard was put forward by the National Technical Committee for Standardization of Metallic and Non-metallic Coverings. This standard was drafted by the 31st Institute of the Third Academy of the Ministry of Aerospace Industry. The main drafters of this standard are Hu Meihua, Pei Erquan, and Zhang Jiahua.
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