Corrosion is the destruction or deterioration of materials or their properties caused by the environment. Most of the corrosion occurs in the atmospheric environment. The atmosphere 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 corrosion of salt spray on the surface of metal materials is caused by the electrochemical reaction between the chloride ion contained in the oxide layer and the protective layer of the metal surface and the internal metal. At the same time, chloride ions contain a certain amount of hydration energy, which can easily be adsorbed on the pores and cracks of the metal surface to squeeze out and replace the oxygen in the oxide layer, turning insoluble oxides into soluble chlorides, and turning the passivated surface into an active surface .

Salt spray test is an environmental test that mainly uses artificially simulated salt spray environmental conditions created by salt spray test equipment to assess the corrosion resistance of products or metal materials. It is divided into two categories, one is the natural environment exposure test, and the other is the artificial accelerated simulated salt spray environment test. The artificial simulated salt spray environment test is to use a kind of test equipment with a certain volume space-salt spray test box, in its volume space, artificial methods are used to create a salt spray environment to assess the quality of the salt spray corrosion resistance of the product . Compared with the natural environment, the salt concentration of chloride in the salt spray environment can be several or tens of times the salt spray content of the general natural environment, which greatly increases the corrosion rate. The salt spray test of the product is carried out and the result is obtained The time is also greatly shortened. For example, if a product sample is tested in a natural exposure environment, it may take 1 year to wait for its corrosion. However, the test under artificial salt spray environment conditions requires only 24 hours to obtain similar results