Corrosion is the destruction or deterioration of a material or its properties under the action of the environment. Most corrosion occurs in the atmospheric environment, which contains corrosive components and factors such as oxygen, humidity, temperature changes and pollutants. Salt spray corrosion is a common and most destructive atmospheric corrosion. The salt fog mentioned here refers to the atmosphere of chloride, and its main corrosion component is the chloride salt in the ocean - sodium chloride, which mainly comes from the ocean and inland saline-alkali areas. The corrosion of salt spray on the surface of metal materials is caused by the electrochemical reaction of the chloride ions contained in the metal surface through the oxide layer and protective layer of the metal surface and the internal metal. At the same time, chloride ions contain a certain amount of hydration energy, and are easily absorbed by pores and cracks on the metal surface to displace and replace oxygen in the chlorinated layer, turning insoluble oxides into soluble chlorides, and making the passivated surface active. surface. Cause very bad adverse reactions to the product.
Salt spray test is an environmental test that mainly 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 natural environmental exposure test, and the other is 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 - the salt spray test box, in its volume space, artificial methods are used to create a salt spray environment to assess the product's salt spray corrosion resistance performance and quality. Compared with the natural environment, the salt concentration of chloride in the salt spray environment can be several times or dozens of times that of the general natural environment, which greatly increases the corrosion rate. The salt spray test is carried out on the product to obtain the result. 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 it to corrode, while in the artificial simulated salt spray environment, it only takes 24 hours to obtain similar results.
3. Salt spray test standards and determination of test results
The salt spray test standard is a uniform specification for repetitive objects and overviews among ort test. The salt spray test standard is a clear and specific regulation for the salt spray test conditions, such as temperature, humidity, sodium chloride solution concentration and pH value, etc., and also puts forward technical requirements for the performance of the salt spray test chamber. Which salt spray test standard is used for the same product should be selected according to the characteristics of the salt spray test, the corrosion rate of the metal and the sensitivity to salt spray. Several salt spray test standards are introduced below, such as GB/T2423.17-1993 "Basic Environmental Test Procedures for Electrical and Electronic Products Test Ka: Salt Spray Test Method", GB/T2423.18-2000 "Electrical and Electronic Products Environmental Test Part 2" : Test Kb: Salt Spray, Alternating (Sodium Chloride Solution)", GB5938-86 "Test Method for Corrosion Resistance of Metal Coatings and Chemically Treated Layers of Light Industrial Products", GB/T1771-91 "Neutral Resistance of Paints and Varnishes" Determination of Salt Spray Properties.
The purpose of the salt fog test is to assess the salt spray corrosion resistance quality of the product or metal material, and the judgment of the salt fog test result is the judgment of the product quality. key to quality.