This standard specifies the test solutions, equipment and methods used in the salt water drop corrosion test of metal and non-organic coatings on metal substrates. This standard is applicable to the detection of defects in negative polarity metal coatings, and is also applicable to the detection of the quality of chemical or electrochemical conversion films obtained by treatment with methods such as chromate and phosphate. This standard is not applicable to coatings used in harsh environments. The test results obtained in this standard cannot be used as a basis for the corrosion resistance of the tested coating in the use environment, nor can they be used as a basis for comparing the corrosion resistance of different coatings in use. JB/T 7702-1995 Salt water drop corrosion test of metal and non-organic coatings on metal substrates (SD test) JB/T7702-1995 Standard download decompression password: www.bzxz.net
This standard specifies the test solutions, equipment and methods used in the salt water drop corrosion test of metal and non-organic coatings on metal substrates. This standard is applicable to the detection of defects in negative polarity metal coatings, and is also applicable to the detection of the quality of chemical or electrochemical conversion films obtained by treatment with methods such as chromate and phosphate. This standard is not applicable to coatings used in harsh environments. The test results obtained in this standard cannot be used as a basis for the corrosion resistance of the tested covering in the service environment, nor can they be used as a basis for comparing the corrosion resistance of different coverings in service.

Mechanical Industry Standard of the People's Republic of China
JB/T 7702-95
Salt water drip corrosion test for metal and non-organic coatings on metal substrates (SD test)
Published on June 20, 1995
Published by the Ministry of Machinery Industry of the People's Republic of China
Implemented on January 1, 1996
Mechanical Industry Standard of the People's Republic of China
Salt water drip corrosion test for metal and non-organic coatings on metal substrates (SD test)
JB/T 7702-95
This standard is equivalent to the international standard ISO4536-1985 "Salt water drip corrosion test for metal and non-organic coatings on metal substrates"
(SD test).
Subject content and scope of application
This standard specifies the test solution, equipment and method used in the salt water drip corrosion test for metal and non-organic coatings on metal substrates. This standard is applicable to the detection of defects in cathodic metal coatings, and is also applicable to the detection of the quality of chemical or electrochemical conversion films obtained by treatment with chromate and phosphate. This standard is not applicable to coatings used in harsh environments. The test results obtained in this standard cannot be used as a basis for the corrosion resistance of the tested coating in the use environment, nor can they be used as a basis for comparing the corrosion resistance of different coatings in use. 2 Reference Standards
Rating of Electroplated Specimens after Corrosion Test of Metal Coatings on Coatings with Cathodic Substrates GB 6461
3 Test Solution
Use analytically pure reagents and distilled or deionized water with a pH of 6.5 to 7.2 to prepare the test solution. The composition is shown in Table 1. Table 1 Composition of test solution
Sodium chloride NaCl
Magnesium chloride
MgCl2
Magnesium sulfate
MgSO4
Calcium chloride
CaCl2
Potassium chloride KCI
Sodium hydrogen phosphate NaHCO3
Sodium bromide NaBr
Before use, the solution needs to be filtered to prevent solid matter from clogging the nozzle. 4 Equipment
4.1 Spray device
Includes a container for the test solution, a nozzle that can produce an appropriate spray, and a pressure device. A suitable manually operated spray device is recommended, see Appendix B (reference). Concentration
26.5
0.73
0.20
0.28
4.2 Stand
Used to fix the sample. The test stand is made of non-metallic materials (such as glass or plastic) that are resistant to corrosion by the test solution. Approved by the Ministry of Machinery Industry on June 20, 1995
Implemented on January 1, 1996
4.3 Test Chamber
JB/T 7702-95
Unless otherwise specified, the temperature in the test chamber is 23℃ and the relative humidity is 85% to 95%. The test chamber can be of appropriate type and size and made of corrosion-resistant materials (such as glass or plastic) to prevent contamination of the specimen. The required relative humidity can be generated and maintained by an open container containing water or a saturated salt solution (such as potassium chloride or potassium nitrate) that does not affect the corrosion process placed at the bottom of the chamber.
5 Test Specimens
5.1 The type, quantity, shape and size of the test specimen shall be determined according to the requirements of the test cover or product standard. If there is no standard, it can be determined by negotiation between the two parties to the test.
5.2 Before the test, the specimen must be fully cleaned. The cleaning method depends on the surface condition of the sample and the nature of the dirt. Abrasives and solvents that will corrode the sample or form a surface film should not be used during cleaning. After the sample is cleaned, it must be free of contamination. 5.3 If the sample is cut from a workpiece, the covering layer must not be damaged, especially the covering layer near the cutting area. Unless otherwise specified, the edges of the sample must be protected with appropriate materials such as paint, paraffin or adhesive tape. 6 Sample placement
6.1 After spraying, the sample is placed on the stand. The sample cannot contact the box wall or other objects in the box, and the samples cannot contact each other. The test solution does not flow from one sample to another. 6.2 The test surface can be tilted at any angle, but it must be ensured that the droplet dispersion required by 7.1 can be maintained during the test. 7 Test process
7.1 Use a spray device to gently spray the test solution onto the sample. The spray droplets should be evenly distributed on the entire test surface. The size and distribution requirements of the droplets are shown in Appendix A (Supplement). The droplets cannot form a continuous film on the test surface. If droplet aggregation occurs, re-spraying shall be performed. Before re-spraying, the droplets shall be washed off and the specimen shall be dried.
7.2 After spraying, the specimen shall be immediately placed on a stand in a test chamber that has reached the specified temperature and relative humidity. Avoid sudden changes in temperature and humidity as much as possible. 7.3 Check the specimen at least once every 24 hours. When checking, remove the specimen from the chamber and check it for as short a time as possible. Do not allow the droplets to dry and do not damage the accumulation of salt and corrosion products. During the inspection, if the droplet size and number are found to be reduced, re-spraying shall be performed in accordance with the provisions of 7.1. 7.4 After the test, the specimen shall be cleaned and inspected in accordance with the method specified for the tested covering or product. The residual mist on the surface shall usually be removed, such as gently rinsing or immersing in clean running water at a temperature not exceeding 40°C, and then immediately drying with a hair dryer. Damage or shedding of corrosion products shall be avoided.
8 Test cycle
The test cycle shall be determined by the tested covering or product standard. The recommended test cycle is 2.6, 24, 48, 96, 240, 480.720h. 9 Evaluation of test results
The test result evaluation method shall be in accordance with the standards of the tested covering layer or product. Generally, the following points shall be considered: Time of corrosion onset:
Appearance of the sample before cleaning after the test. Appearance of the sample after cleaning; c.
Appearance of the sample after the corrosion product is removed
d. The number and distribution of corrosion defects (such as pitting, cracks, bubbles, etc.), and the corrosion level shall be evaluated according to GB6461. 10 Test report
10.1i
The test report must state the evaluation criteria adopted and the test results obtained. If necessary, there shall be the results of each sample, the average results of each group of parallel 2
specimens or photos of the samples. JB/T 7702-95
The test report must include information on the test method, which may be determined according to the purpose of the test and its requirements. Generally includes the following 10.2
Contents:
Description of the tested covering layer or product:
Shape and size of the test specimen·Area and surface condition of the test specimen: Preparation of the test specimen, including cleaning before the test and protection of the edges or other special parts of the test specimen; Number of test specimens;
Cleaning method of the test specimen after the test·If necessary, the weight loss caused by cleaning should be explained; Composition of the test solution, number of sprays during the test; Temperature and relative humidity in the test chamber and their fluctuation range: Test time;
In order to verify the accuracy of the test conditions, the properties of the reference test piece placed in the test chamber and the results obtained. 3
JB/T 7702-95
Appendix A
Requirements for spray droplet size and distribution
(Supplement)
A1 The requirements for spray droplet size and distribution are shown in Figure A1b, and Figure A1a and ℃ do not meet the requirements. If the droplet pattern is difficult to see clearly due to the roughness or color of the sample surface, you can first test spray on a clean, smooth metal, glass or plastic sample. When the spray droplets meet the requirements, spray on the test surface with the same operation. 088388882
Figure A1 Requirements for spray droplet size and distribution
JB/T 7702--95
Appendix B
Manually operated spray device
(reference)
B1 A suitable manually operated spray device is recommended, see Figure B1. Figure B1
Manually operated spray device
Additional notes:
This standard was proposed by the National Technical Committee for Standardization of Metal and Non-metal Coverings. This standard was drafted by the Wuhan Institute of Materials Protection of the Ministry of Machinery Industry. The main drafters of this standard were Xia Chunlan and Fang Yisan. 5
People's Republic of China
Mechanical Industry Standard
Salt water drop corrosion test for metal and non-organic coating on metal substrate (SD test)bzxz.net
JB/T 7702-95
Published by the Machinery Standardization Research Institute of the Ministry of Machinery Industry Printed by the Machinery Standardization Research Institute of the Ministry of Machinery Industry (PO Box 8144, Beijing 100081)
No reproduction
Copyright reserved
Format 880×12301/16
Printing sheet 1/2
Number of words 10,000
First edition in January 1996 First printing in January 1996 Print run 00.001-500 Price 5.00 yuan
No.95-001
L/ar
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