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1. Corrosion of salt and fog
Corrosion is destruction or deterioration caused by the material or its performance under the action of the environment. Most corrosion occurs in the atmospheric environment, and the atmosphere contains corrosive ingredients and corrosion factors such as oxygen, humidity, temperature changes, and pollutants. Salt erosion is a common and most destructive atmospheric corrosion. The salt mist mentioned here refers to the atmosphere of chloride. Its main corrosion ingredients are chloride salt -sodium chloride in the ocean. It mainly comes from saline -alkali areas in the ocean and mainland. The corrosion of salt fog on the surface of the metal material is caused by electrochemical reactions of the oxidation layer and protective layer contained in the metal surface with chloride ions contained in the metal surface. At the same time, chloride ions contain a certain hydrophobic energy, which is easily adsorbed on the pores on the metal surface, the cracks are crowded and replaced the oxygen in the chlorine layer, turning insoluble oxides into soluble chloride, making the passivation surface become lively surface. Causes bad reactions to the product.
2. Salt Mist test and connection with actual reality
salt fog test is a manual created by the salt fog test equipment Simulation of the environmental test of the environmental test of the salt and mosaic environmental or metal materials. It is divided into two categories, one is a natural environment exposure test, and the other is artificially accelerating the simulation of salt fog environmental tests. The artificial simulation of the salt fog environment test is the use of a test equipment with a certain volume space -a salt fog test box, which uses an artificial method in its volume space to assess the salt -resistant corrosion performance quality of the product Essence Compared with the natural environment, the salt concentration of the chloride of its salt and mist environment can be several times or dozens of times of the content of salt and fog content in the average natural environment, which greatly improves the corrosion speed. The time is also greatly shortened. If a sample of a product is tested in a natural exposure environment, it may take 1 year after its corrosion, and test under the conditions of artificial simulation of salt fog, as long as 24 hours, you can get similar results.
Artificial simulation salt fog test also includes neutral salt fog tests, acetate fog tests, copper salt acceleration acetate fog tests, and alternative salt fog tests.
(1) Neutral salt fog test (NSS test) is the earliest most widely used accelerated corrosion test method. It uses 5%sodium chloride saline solution, and the pH value of the solution is adjusted in a neutral range (6-7) as a solution for spray. The test temperature is taken at 35 ° C, and the sedimentation rate of the salt mist is required to be between 1-2ml/80cm2.h.
(2) The acetate mist test (ASS test) developed on the basis of a neutral salt fog test. It adds some methamphetamine to 5%sodium chloride solution to reduce the pH value of the solution to about 3, the solution becomes acidic, and the final salt mist also changes from neutral salt mist to acidic. Its corrosion speed is 3 times faster than the NSS testabout.
(3) Copper salt accelerated acetate fog test (CASS test) is a newly developed fast salt fog corrosion test developed in foreign countries. Add a small amount of copper -salt -copper chloride, which ly induces corrosion. Its corrosion speed is about 8 times the NSS test.
(4) Salt mogo test is a comprehensive salt fog test. It is actually a neutral salt fog test plus constant damp heat test. It is mainly used for the entire machine product of the cavity. Through the infiltration of the moisture environment, the corrosion of salt fog is not only produced on the surface of the product, but also inside the product. It alternate the product under the environment of salt and fog and damp heat, and finally evaluates whether the electrical performance and mechanical properties of the entire machine product have changed.
Third, the judgment of the test criteria and test results of salt fog
The standard is a unified provision of repetitive things and overview. The salt fog test standard is to make the salt fog test conditions, such as temperature, humidity, sodium chloride solution concentration and pH value, etc., and also propose technical requirements for the performance of the salt fog test box. The same product uses that kind of salt and mist test standards according to the characteristics of salt fog tests and the corrosion speed of metal and the degree of sensitivity to salt fog. Here are a few salt fog test standards, such as IOS2423.17-1993 Basic Environmental Test Regulations Test KA: Salt Mist Test Method, IOS2423.18-2000 Electrical Electronic Product Environment Test Part 2 2 : Test test KB: Salt Mist, Intercourse (Sodium Chloride solution) , GB5938-86 Method of Metal Plating and Chemical Treatment Layer , IOS1771-91 Measurement of Sexual Salt Misty Performance .
The purpose of the salt fog test is to assess the salt -resistant corrosion quality of the product or metal material, and the judgment of the salt fog test results is the judgment of the product quality. Correct and reasonable is the key to correctly measure the quality of products or metal anti -salt fog corrosion. The method of judging the results of the salt fog test results include: rating judgment, weighing judgment method, corrosion judgment method, and corrosion data statistical analysis method.
