Salt spray experiment
Salt spray corrosion is a common and most destructive atmospheric corrosion. Salt spray in daily life refers to the atmosphere containing chloride. Its main corrosive component is sodium chloride from the water vapor in the ocean and inland saline-alkali areas. It causes corrosion to metals through atmospheric flow and rainwater moisture. Corrosion is mainly caused by the electrochemical reaction between chloride ions penetrating the oxide layer and protective layer on the metal surface and the internal metal. At the same time, chloride ions have certain hydration properties and are easily absorbed by the pores and cracks on the metal surface to crowd out and replace the oxygen in the oxide layer, turning insoluble oxides into soluble chlorides, turning the passive surface into an active surface. Cause adverse reactions that damage the product.
Salt spray test is an environmental test that mainly uses artificial simulated salt spray environmental conditions created by salt spray testing equipment to evaluate the corrosion resistance of products or metal materials. It is divided into two categories, one is natural environment exposure test, and the other is 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 use artificial methods in its volume space to create a salt spray environment to evaluate the salt spray corrosion resistance performance and quality of the product. . Compared with the natural environment, the salt concentration of chloride in the salt spray environment can be several or dozens of times that of the general natural environment, which greatly increases the corrosion rate, so that the product can be estimated in a short time. Corrosion resistance under long-term use under natural conditions.
Generally, salt spray experiments mostly refer to artificial simulated salt spray tests, which are classified as follows:
1 Neutral salt spray test ( NSS test)
It is the earliest accelerated corrosion test method that has the widest application field. It uses 5% sodium chloride salt solution, and the pH value of the solution is adjusted to the neutral range ( 6 to 7 ) as the spray solution. The test temperature is all 35℃ , and the sedimentation rate of salt spray is required to be between 1 ~ 2ml/80cm2.h .
2 Acid salt spray test ( ASS test)
It is developed on the basis of neutral salt spray test. It is to add some glacial acetic acid to a 5% sodium chloride solution to reduce the pH value of the solution to about 3 , the solution becomes acidic, and the salt spray formed also changes from neutral salt spray to acidic. Its corrosion rate is about 3 times faster than the NSS test .
3 Copper salt accelerated acetate salt spray test ( CASS test)
It is a rapid salt spray corrosion test recently developed abroad. 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 approximately 8 times that of the NSS test .
4 Alternating (cyclic) salt spray test
It is a comprehensive salt spray test, which is actually a neutral salt spray test plus a constant humidity and heat test. It is mainly used for cavity-type complete machine products. Through the penetration of the moist environment, salt spray corrosion occurs not only on the surface of the product, but also inside the product. It alternately converts the product under two environmental conditions: salt spray and humid heat, and comprehensively assesses whether there are any changes in the electrical and mechanical properties of the complete product.
5 Water mist test and humidity resistance test
It is a product's water and moisture corrosion resistance test, which simply tests the water resistance of the product. Generally, the effect of this type of test is relatively mild and is closer to the natural environment exposure test.
Common standards for salt spray testing:
GB/T 2423.17; GB.T 2423.18; GB/T 10125; GB/T 6461; GB/T 12967.3; GB 6458; ISO 4628.3; ISO 9227; ISO 3768; DIN EN ISO 7253;
IEC 60068-2-52; IEC 60068-2-11; BS 3900-F12; BS 7479
ASTM B 117; ASTM B368-09; DIN 50021; BS 7479
EIA-364-26B; JIS Z2371; GJB 150.1; MIL-STD-883E
Zhongyu Testing has specialized in carrying out various salt spray testing services for more than ten years and has rich experience in salt spray corrosion testing services. At the same time, it can coordinate a wide range of domestic and foreign laboratory resources to meet salt spray testing requirements at different times in a timely manner, and provides a wide range of services around the world. The recognized and authoritative test report is well received and trusted by our customers.