According to the description of the salt spray test mechanism, the salt spray test can be divided into two categories: natural environment exposure test and artificial accelerated simulated salt spray environment test.
Compared with the natural environment, the chloride concentration in the artificial salt spray environment can reach several times or dozens of times the salt spray content in the general natural environment, which greatly increases the corrosion rate and greatly shortens the salt spray test time of the product. If a product sample is tested in a natural exposure environment, corrosion may take a year, while in an artificially simulated salt spray environment, similar results can be obtained within 24 hours.
The artificial simulated salt spray test includes neutral salt spray test, acetic acid salt spray test, copper salt accelerated acetate salt spray test and alternating salt spray test.
1. Neutral salt spray test
Under normal circumstances, it uses 5% NaCl solution and adjusts the pH value to a neutral range (6.5 to 7.2) as a spray solution. The test temperature is 35 (°C). The settling rate of salt mist is required to be between 1-3 ml/80 cm 2.h, and the settling amount is usually between 1-2 ml/80 cm 2.h.
2. Acetic acid spray test
Pour glacial acetic acid into a 5% sodium chloride solution to lower the pH of the solution to about 3, making the solution acidic and finally changing the salt spray from neutral to acidic. It corrodes about three times faster than the NSS test.
3. Copper salt accelerated acetic acid salt spray test
This is a quick salt spray corrosion test. The test temperature is 50°C. A small amount of copper salt - copper chloride is added to the salt solution for strong corrosion. Its corrosion rate is about eight times that of the NSS test.
4. Alternate salt spray test
This is a full salt spray test, which is actually a neutral salt spray test plus constant humidity and heat testing. It is mainly used for hollow mechanical products. Through the penetration of tidal environment, salt spray corrosion will not only occur on the surface of the product, but also inside the product. It uses the product alternately under conditions of salt spray, humidity and heat, and finally checks whether the electrical and mechanical properties of the entire product have changed.
