How long is one hour of salt spray test equivalent to natural environment?
Salt spray test 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 is to use a test equipment with a certain volume space - salt spray test chamber, and use the artificial method to create a salt spray environment in its volume space to assess the quality of salt spray corrosion resistance of products. Compared with the natural environment, the salt concentration of chloride in the salt spray environment can be several times or dozens of times of the salt spray content in the general natural environment, which greatly improves the corrosion rate. The salt spray test on the product also greatly shortens the time to obtain the results. If a product sample is tested in a natural exposure environment, it may take 1 year to be corroded. However, if it is tested in a simulated salt spray environment, similar results can be obtained as long as 24 hours.
The artificial salt spray test includes neutral salt spray test, acetate spray test, copper salt accelerated acetate spray test and alternating salt spray test.
(1) Neutral salt spray test (NSS test) is one of the earliest accelerated corrosion test methods in the field of application. It uses 5% sodium chloride saline solution, and the pH value of the solution is adjusted to the neutral range (6 ~ 7) as the solution for spray. The test temperature is 35 ℃, and the sedimentation rate of salt spray is required to be 1 ~ 2ml/80cm ². H.
(2) Acetate spray test (ASS test) is developed on the basis of neutral salt spray test. It is to add some glacial acetic acid to the 5% sodium chloride solution, so that the pH value of the solution is reduced to about 3, the solution becomes acidic, and the finally formed salt mist also becomes acidic from neutral salt mist. Its corrosion rate is about 3 times faster than that of NSS test.
(3) Copper salt accelerated acetate spray test (CASS test) is a newly developed rapid salt spray corrosion test abroad. The test temperature is 50 ℃, and a small amount of copper salt - copper chloride is added to the salt solution to strongly induce corrosion. Its corrosion rate is about 8 times that of NSS test.
The specific time is converted into:
Neutral salt spray test 24h ⇌ natural environment 1 year
Acetate fog test 24h ⇌ natural environment 3 years
Copper salt accelerated acetate spray test 24h ⇌ 8 years in natural environment