The neutral salt spray test chamber is an environmental test that uses artificial simulated salt spray environmental conditions created by salt spray test equipment to evaluate the corrosion resistance of products or metal materials. It is divided into two categories, one is the natural environmental exposure test, and the other is the artificial accelerated simulated salt spray environment test. The artificial simulated salt spray environment test uses a test equipment with a certain volume space, the salt spray test chamber, to artificially use the salt spray environment in the volume space to assess the salt spray corrosion resistance quality of the product. . Compared with the natural environment, the salt concentration of the chloride in the salt spray environment can be several times or several times that of the salt spray content of the general natural environment, so that the corrosion rate is greatly improved, and the product is subjected to a salt spray test to obtain a result. The time is also greatly shortened. If a product sample is tested in a natural exposure environment, it may take 1 year to corrode, and in a simulated simulated salt spray environment, as long as 24 hours, similar results can be obtained.
Corrosion is the destruction or deterioration of a material or its properties caused by the environment. Most of the corrosion occurs in the atmosphere, which contains corrosive components and corrosive factors such as oxygen, humidity, temperature changes, and pollutants. Salt spray corrosion is a common and most destructive atmospheric corrosion. The salt spray mentioned here refers to the atmosphere of chloride. Its main corrosive component is the chloride salt in the ocean, sodium chloride, which is mainly derived from the ocean and the saline-alkali areas in the interior. The corrosion of the surface of the metal material by the salt spray is caused by the electrochemical reaction of the chloride layer which penetrates the metal surface and the protective layer and the internal metal. At the same time, chloride ions contain a certain hydration energy, which is easily adsorbed on the pores of the metal surface, and the cracks are displaced and replace the oxygen in the chlorinated layer, turning the insoluble oxide into a soluble chloride, making the passivated surface active. surface. Causes a bad reaction to the product.
The artificial simulated salt spray test includes a neutral salt spray test, an acetate salt spray test, a copper salt accelerated acetate spray test, and an alternating salt spray test.
1. Neutral salt spray test (NSS test) is one of the earliest applications in the field of accelerated corrosion test. It uses a 5% aqueous solution of sodium chloride solution, and the pH of the solution is adjusted to a neutral range (6-7) as a solution for spraying. The test temperature is taken at 35 ° C, and the sedimentation rate of the salt spray is required to be between 1 and 2 ml / 80 cm 2 · h.
2. The acetate spray test (ASS test) was developed on the basis of a neutral salt spray test. It is to add some glacial acetic acid to the 5% sodium chloride solution, the pH value of the solution is reduced to about 3, the solution becomes acidic, and the salt mist formed finally changes from neutral salt spray to acidity. Its corrosion rate is about 3 times faster than the NSS test.
3. Copper salt accelerated acetate spray test (CASS test) is a rapid salt spray corrosion test developed recently in foreign countries. The test temperature is 50 ° C. A small amount of copper salt - copper chloride is added to the salt solution to strongly induce corrosion. Its corrosion rate is about 8 times that of the NSS test.
4. The neutral salt spray test chamber alternately converts the product under salt water and humid heat conditions, and finally checks whether the electrical properties and mechanical properties of the whole product are changed. The alternating salt spray test is a comprehensive salt spray test which is actually a neutral salt spray test plus a constant damp heat test. It is mainly used in cavity-type machine products. Through the penetration of the tidal environment, salt spray corrosion is generated not only on the surface of the product, but also inside the product.
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