1. Brief introduction of salt spray corrosion:
Corrosion is the destruction or deterioration of materials or their properties caused by the environment. Most corrosion occurs in the atmospheric environment, and the atmosphere contains corrosive components and factors such as oxygen, humidity, temperature changes, and pollutants.
Salt spray corrosion is a common and most destructive atmospheric corrosion. Salt mist refers to the atmosphere of chloride, and its main corrosive component is sodium chloride.
2. The mechanism of salt spray corrosion:
The corrosion of the metal material surface caused by salt spray is caused by the electrochemical reaction of chloride ions penetrating the oxide layer and the protective layer on the metal surface and the internal metal. At the same time, the chloride ion contains a certain hydration energy, which is easily squeezed out by the pores and cracks adsorbed on the metal surface and replaces the oxygen in the chloride layer. Surface, causing an adverse reaction to the product.
Anode: The metal loses electrons and becomes a metal cation, and enters the solution in the form of hydrated ions while leaving considerable electrons in the metal.
Cathode: The remaining electrons left in the cathode metal are depolarized by oxygen, reducing and absorbing the electrons to become hydroxide ions.
Electrolyte: sodium chloride dissociates to generate sodium ions and chloride ions, and some chloride ions, metal ions and hydroxide ions react to form metal corrosives.
3. The hazard of salt spray corrosion:
1) Salt spray corrosion will destroy the metal protective layer, make it lose its decorativeness, and reduce its mechanical strength;
2) Some electronic components and electrical circuits are interrupted by power lines due to corrosion, especially in vibrating environments;
3) When the salt mist falls on the surface of the insulator, the surface resistance will be reduced; after the insulator absorbs the salt solution, its volume resistance will be reduced by four orders of magnitude;
4) The moving parts of mechanical parts or moving parts increase the friction due to the generation of corrosive substances, which may cause the moving parts to be stuck.
4 Metal material salt spray corrosion test:
The salt spray test is divided into a natural environment exposure test and an artificial accelerated simulated environment test. The latter uses a salt spray test box and uses a manual method in its volume space to create a salt spray environment to conduct the salt spray corrosion resistance quality of products. Assessment.
Test a product sample in a naturally exposed environment, and it may take one year to corrode the corrosion. Naturally, it takes time to wait, and the test under artificially simulated salt spray environment conditions can obtain similar results as long as 24 hours. However, the artificial accelerated simulation test is still different from the natural environment, so it cannot be replaced.
The artificial accelerated simulated environment test is to use a salt spray test chamber with a certain volume of space to create a salt spray environment by artificial methods in its volume space, and to evaluate the quality of the salt spray corrosion resistance of components. Common salt spray test chamber tests can be divided into four categories: neutral salt spray test, acetate salt spray test, copper accelerated acetate salt spray test, alternating salt spray test.
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