Test methods for corrosion of metallic coatings and chemically treated layers
Some standard content:
Standard of the Fourth Machinery Industry Department of the People's Republic of China
Metallic coatings and chemical treatment layers
Corrosion test methods
SJ1283-77
The scope of application of the four corrosion test methods listed in this standard are: neutral salt spray and acetate spray corrosion test methods are applicable to the inspection of the corrosion resistance of anodic or cathodic metal coatings and chemical treatment layers; copper accelerated acetate spray corrosion test method is mainly applicable to the inspection of decorative copper-nickel-chromium or nickel-chromium layers on steel parts and zinc die castings, It is also suitable for testing the anodized layer of aluminum and aluminum alloys. The corrosion test method is suitable for testing the corrosion resistance of decorative chrome coatings, mainly copper-nickel-chromium and nickel-galvanneal coatings.
I. Neutral salt spray corrosion test method
(I) Equipment
1. The test equipment consists of a spray chamber, a salt water reservoir, a compressed air supply (including purification) system, a nozzle, a sample holder, and heating and other necessary control means. If the conditions obtained can meet the requirements of this method, the size and detailed structure of the equipment are not restricted.
2. The structural materials in the test equipment should not affect the corrosion performance of salt spray, and at the same time be resistant to salt spray corrosion.
3. The droplets condensed on the top of the spray chamber are not allowed to be sprayed directly onto the sample. 4. A baffle is provided in the box to prevent the salt from being sprayed directly onto the sample. (II) Samples
5. Sample preparation: Clean the samples. The cleaning method can be selected according to the surface and the nature of the oil stains. However, solvents that can react chemically with the substrate and the coating should not be used. 6. The sample should be placed in the box so that the main surface to be tested is at an angle of 15-30° to the vertical line and parallel to the main direction of the salt spray flow in the box. At the same time, the sample should be placed so that the salt spray can settle freely on all samples. The salt solution on one sample should not drip onto any other sample. Page 2 of 8
During the test, it must be noted that the samples should not contact each other or other metals or absorbent materials
7. The cut edges of the samples or the places with identification marks should be coated with anti-corrosion materials with appropriate materials.
8. The samples should be placed when the temperature in the box is close to the test temperature. (III) Preparation of salt spray solution
9. Dissolve 50±1g of chemically pure sodium nitride in 1L of steamed filling water. If there are suspended or precipitated particles, they should be filtered or decanted before pouring. 10. The pH value of the solution can be adjusted to 6.5-7.2 with chemically pure hydrochloric acid or sodium hydroxide. To eliminate the influence of temperature on the pH value, when measuring and adjusting the pH value of the solution, the solution should be boiled for half a minute, then cooled and adjusted, or the solution should be kept at 35°C for more than 48 hours before adjustment.
11. The solution dripped from the sample cannot be used for spraying. (IV) Test conditions
12. The test temperature is 35±2°C.
13. Salt spray deposition rate: At least two clean fog collectors should be placed in the exposure area of the box. One should be close to the nozzle and the other should be placed farthest from the nozzle. Droplets from the sample or any other source are not allowed to be collected in the collector. Based on the average value of continuous spraying for 8 hours, the salt spray deposition rate should be 0.5-2 ml/hour/80 cm3
A suitable mist collector is a 10 cm diameter funnel or crystallizer inserted in the volume (cutting area is about 80 cm3).
14. The collected mist liquid should contain 50 ± 10 g/L of sodium chloride (that is, the specific gravity should be 1.0255-1.0400 g/cm3), and the pH value should be 6.5-7.2.15. The nozzle pressure should be 0.07-0.175 g/cm216. Spraying method: Spray continuously for 8 hours, then stop heating, stop spraying, and keep it in a static and closed state for 16 hours, with a total of 24 hours as a cycle. (V) Cleaning and inspection of samples
17. After the test, carefully remove the sample from the salt spray chamber, wash it gently with running cold water to remove salt deposits from the surface, and then dry it immediately, and promptly check the degree of corrosion or 2
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Other defects.
SJ1283-77
(VI) Test cycle and quality assessment
18. The test cycle and quality requirements of various metal coatings and chemical treatment layers of different thicknesses shall be specified in the relevant material or product technical conditions, and the corrosion rating shall be carried out in accordance with SJ1284--77. 19. For the test cycle and quality assessment of certain metal coatings and chemical treatment layers, please refer to the appendix. Appendix
Technical requirements for neutral salt spray corrosion test of zinc-cadmium coatings on steelCoating category
First category
(without chromic acid
passivation)
Second category
(with chromic acid
passivation)
First category
(without chromic acid
passivation)
Second category
(with chromic acid
passivation)
Minimum coating thickness (micrometer)
Technical requirements for neutral salt spray test
No base metal corrosion for 48 hours
No base metal corrosion in 120 hours
No base metal corrosion in 216 hours
No white rust in 96 hours
No white rust in 96 hours
No white rust in 96 hours
No white rust in 120 hours
No base metal corrosion in 240 hours
No base metal corrosion in 384 hours
White rust in 96 hours
No white rust in 96 hours
No white rust in 96 hours
Check the passivation film
Check the passivation film
Check the passivation film Quality plate
Check the quality of the passivation film
Check the quality of the passivation film
SJ1283-77
Appendix II
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Technical requirements for neutral salt spray corrosion test of anodized and chemically oxidized (or phosphated) films of aluminum and aluminum alloys
Coating category
Anodized
After anodized
Chromate sealing
Chemical oxidation or phosphating
Technical requirements for salt spray resistance test
No corrosion pits appear for 144 hours
168 hours No corrosion spots appear for 96 hours
No corrosion spots appear for 96 hours
Technical requirements for neutral salt spray corrosion test of copper-nickel-chromium layer on steel
Lock pot
Minimum thickness of copper layerbzxz.net
Test time
(hours)
Quality assessment
Not less than grade 9
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)Equipment
SJ1283-77
II. Acetate mist corrosion test method
1. Same as requirements for neutral salt test equipment (II) Test
2. Same as requirements for neutral salt test specimens.
(III) Preparation of salt spray solution
3. Dissolve 50±1g of chemically inactive sodium fluoride in 1L of distilled water and adjust the pH to 3.0-3.1 with chemically pure glacial acetic acid. The pH value of the solution should be measured with an acidometer. 4. Before the newly prepared salt solution is placed in the storage container, it should be filtered or decanted. There should be no suspended particles before spraying.
5. The solution dripped from the sample cannot be used for spraying. (IV) Test conditions
6. The test temperature, salt spray deposition rate and nozzle pressure are the same as those in Articles 12, 13 and 15 of the neutral salt spray test method.
7. The collected mist should contain 50±10 g/L of sodium fluoride (specific gravity should be 1.0255~1.0400 g/cm3), PH is 3.2±0.1,
8. Spray method: Except for taking out the sample for inspection and adjusting and replenishing the solution for a short time, the test should be carried out continuously within the specified time, (V) Sample processing and inspection
9. Same as Article 17 of the neutral salt spray test method, (VI) Test cycle and quality assessment
10. The test cycle and quality requirements of various metal coatings and chemical treatment layers of different thicknesses should be specified in the relevant material or product technical conditions, and the magic corrosion rating shall be carried out according to SJ1284--77. III. Copper accelerated acetate spray corrosion test method () Equipment
1. Same as the requirements of neutral salt test equipment, but it must be resistant to 50±1℃ test temperature and corrosion resistance of this test solution.
(II) Test specimen
2. Same as the requirements for neutral salt spray test specimen.
(III) Preparation of salt spray solution
SJ1283—77
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3. Dissolve 50±1 g of sodium chloride in 1 liter of distilled water (the pH should be within the range of 6.0-7.0):
4.In each liter of sodium chloride solution, add 0.26 ± 0.02 g CuCl·H2O, and adjust the pH to 3.0-3.1 with glacial acetic acid (pH is measured by an acidometer). 5. The prepared solution should be filtered or decanted into a storage container to remove solid impurities. 6. The chemical reagents used are of chemically pure grade. 7. The solution dripped from the sample cannot be used for spraying. (IV) Test conditions
8. Test temperature: 50 ± 1°C.
9. Salt spray deposition rate: the same as the neutral salt test conditions in Article 13. 10. The collected mist: should contain 50 ± 10 g/L of sodium chloride (that is, the specific gravity should be 1.0255~1.0400 g/cm3), and the pH should be 3.2 ± 0.1. 11. Nozzle pressure: 0.07~0.105 g/cm2 Spray mode: In addition to checking and removing the sample and adjusting or replenishing the salt solution, spraying should be continuous within the specified time.
(V) Cleaning and inspection of samples
13. After the test, carefully remove the sample and wash it in running warm water (up to 38°C) to remove the salts deposited on the surface of the sample, then dry it and promptly check the degree of corrosion or other defects. For steel parts, in order to prevent the disappearance or washing of small rust spots or rust spots, they should be dried for 30-60 minutes after being taken out of the box before cleaning. Check the appearance of the metal coating surface. If there is corrosion, roll off the corrosion products, then wash and dry it. (VI) Test cycle and quality evaluation
14. The test cycle and quality requirements of various metal coatings and chemical treatment layer parts of different thicknesses should be specified in the relevant material or product technical conditions. The corrosion rating shall be carried out in accordance with SJ1284--77.
IV. Corrosion test method
(I) Key points of the method
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SJ1283-77
1. This method is to apply a paste containing corrosive salts on the test sample. After the paste is dry, the sample is placed in a humid chamber with high relative humidity for exposure test. After the specified time, the sample is taken out for inspection and rating.
(II) Equipment
2. Equipment used: humid chamber, sample holder, heating and air circulation system, 3. Fog points on the top, cover or test holder of the humid chamber are not allowed to drip onto the test sample.
4. The structural material of the equipment should not affect the corrosion performance. (III) Preparation of etching paste
5. Preparation of bath solution: Use distilled water or deionized water to prepare the following solutions: (1) Copper nitrate solution: Dissolve 2.5 g of copper nitrate [CuNO3) 2.3H2O) in water and dilute to 500 ml.
(2) Ferric chloride solution: Dissolve 2.5 g of ferric chloride (FeC13·6H2O) in water and dilute to 500 ml (this solution needs to be sealed and stored in a dark place. If it is stored for more than one week, it should not be used again):
(3) Ammonium chloride solution: Dissolve 50 g of ammonium fluoride (NH, C1) in water and dilute to 500 liters.
The above reagents are all chemically pure.
6. Preparation of etching paste:
Take 7.0 ml of the above copper nitrate solution, 33 ml of ferric chloride solution, and 10 ml of ammonium fluoride solution, mix them, add 30 grams of kaolin, and stir with a glass rod for about two minutes until a uniform mud paste is obtained.
The mud paste should be prepared and used immediately. The mud paste prepared according to the above amount can be used to coat about 3 square meters of the sample surface.
(IV) Operation steps
7. Sampling; the type and quantity of the sample are determined according to the technical conditions of the product. 8. Sample preparation. The sample is first cleaned with an appropriate solution such as ethanol, acetone, ether or petroleum ether. Solvents that can react chemically with the substrate and the coating cannot be used. 9. Application of etching paste: Dip a brush or writing brush in the etching paste and make circular movements on the effective surface of the sample to fully apply it. Then, spread it out in one direction with a brush or writing brush to make it evenly flat (the thickness of the corrosive paste on the sample is about 0.05 mm). Then, dry it for 1 hour at room temperature and relative humidity less than 50%. 10. Humidity test: Place the dried sample in a humidity chamber and test it under the following conditions.
(1) The position of the sample in the humidity chamber is not allowed to contact each other, and the bracket cannot contact the surface of the sample coated with the corrosive paste.
(2) Conditions in the humidity chamber: temperature is 38 ± 1°C, relative humidity is 94 ± 4%, and no condensation occurs.
(3) The test cycle and number of cycles are determined by the product technical requirements. If several cycles are required, after the first cycle, the inoculant on the sample can be cleaned with running water and sponge, and then a new paste can be applied as before. 11. Cleaning and inspection of samples: After the wet test, the samples should be carefully removed and processed in time.
(1) If it is a plated sample on a steel part, dry the removed sample and make an assessment of the corrosion rate based on the number of brown rust spots that appear in the mud. If it is necessary to check the damage to the appearance of the sample, the mud can be cleaned with running water and a sponge (soft abrasives can also be used), and then dried for inspection. (2) If it is a sample with a zinc alloy or aluminum alloy substrate, remove the mud with running water and a sponge (soft abrasives can also be used), and then dry it. Based on the number of spots that appear on the base metal due to corrosion, make an assessment of the corrosion rate and check the damage to the appearance. (V) Quality Assessment
12. Evaluate according to the corrosion rating standard SJ1284-778Sampling: The type and quantity of the sample shall be determined according to the technical conditions of the product. 8. Sample preparation: The sample shall be cleaned with an appropriate solution such as ethanol, acetone, ether or petroleum ether in advance. Solvents that can react chemically with the substrate and the coating shall not be used. 9. Coating of the etching paste: Dip the etching paste with a brush or a writing brush and move it in a circular motion on the effective surface of the sample to fully apply it. Then spread it with a brush or a writing brush in one direction to make it evenly flat (the thickness of the etching paste on the sample is about 0.05 mm). Then, dry it for 1 hour at room temperature and relative humidity less than 50%. 10. Humidity test: Place the dried sample in a humidity chamber and test it under the following conditions.
(1) The position of the sample in the humidity chamber requires that it is not allowed to contact each other, and the bracket cannot contact the surface of the sample coated with the etching paste.
(2) Conditions in the humidity chamber: temperature 38 ± 1°C, relative humidity 94 ± 4%, no condensation.
(3) The test cycle and number of cycles are determined by the product technical requirements. If several cycles are required, after the first cycle, the inoculant on the sample can be removed with running water and sponge, and then a new paste can be applied as before. 11. Cleaning and inspection of the sample: After the humidity test, the sample should be carefully removed and processed in time.
(1) If it is a plated sample on a steel part, dry the removed sample and make an assessment of the corrosion rate based on the number of brown rust spots in the paste. If it is necessary to check the damage to the appearance of the sample, clean the paste with running water and sponge (soft abrasives can also be used), dry it, and then inspect it. (2) If it is a sample with a zinc alloy or aluminum alloy substrate, remove the inoculant with running water and sponge (soft abrasives can also be used), and dry it. Make an assessment of the corrosion rate based on the number of spots of corrosion on the base metal and check the damage to the appearance. (V) Quality Assessment
12. Assessment according to corrosion rating standard SJ1284-778Sampling: The type and quantity of the sample shall be determined according to the technical conditions of the product. 8. Sample preparation: The sample shall be cleaned with an appropriate solution such as ethanol, acetone, ether or petroleum ether in advance. Solvents that can react chemically with the substrate and the coating shall not be used. 9. Coating of the etching paste: Dip the etching paste with a brush or a writing brush and move it in a circular motion on the effective surface of the sample to fully apply it. Then spread it with a brush or a writing brush in one direction to make it evenly flat (the thickness of the etching paste on the sample is about 0.05 mm). Then, dry it for 1 hour at room temperature and relative humidity less than 50%. 10. Humidity test: Place the dried sample in a humidity chamber and test it under the following conditions.
(1) The position of the sample in the humidity chamber requires that it is not allowed to contact each other, and the bracket cannot contact the surface of the sample coated with the etching paste.
(2) Conditions in the humidity chamber: temperature 38 ± 1°C, relative humidity 94 ± 4%, no condensation.
(3) The test cycle and number of cycles are determined by the product technical requirements. If several cycles are required, after the first cycle, the inoculant on the sample can be removed with running water and sponge, and then a new paste can be applied as before. 11. Cleaning and inspection of the sample: After the humidity test, the sample should be carefully removed and processed in time.
(1) If it is a plated sample on a steel part, dry the removed sample and make an assessment of the corrosion rate based on the number of brown rust spots in the paste. If it is necessary to check the damage to the appearance of the sample, clean the paste with running water and sponge (soft abrasives can also be used), dry it, and then inspect it. (2) If it is a sample with a zinc alloy or aluminum alloy substrate, remove the inoculant with running water and sponge (soft abrasives can also be used), and dry it. Make an assessment of the corrosion rate based on the number of spots of corrosion on the base metal and check the damage to the appearance. (V) Quality Assessment
12. Assessment according to corrosion rating standard SJ1284-778
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