How long is one hour of salt spray test equivalent to the natural environment?
The salt spray test is divided into two categories, one is the natural environment exposure test, and the other is the 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 quality of the salt spray corrosion resistance of the product . Compared with the natural environment, the salt concentration of chloride in the salt spray environment can be several or tens of times the salt spray content of the general natural environment, which greatly increases the corrosion rate. The salt spray test of the product is carried out and the result is obtained The time is also greatly shortened. For example, if a product sample is tested in a natural exposure environment, it may take 1 year for its corrosion, while the test under artificially simulated salt spray environment conditions requires only 24 hours to obtain similar results.
The artificial simulated salt spray test includes neutral salt spray test, acetic acid salt spray test, copper salt accelerated acetic acid salt spray test, and alternating salt spray test.
(1) The neutral salt spray test (NSS test) is one of the earliest accelerated corrosion test methods with the widest application field. It uses 5% sodium chloride salt aqueous solution, the pH value of the solution is adjusted in the neutral range (6-7) as the spray solution. The test temperature is 35℃, and the sedimentation rate of the salt spray is required to be between 1～2ml/80cm².h.
(2) The acetic acid salt spray test (ASS test) is developed on the basis of the neutral salt spray test. It is to add some glacial acetic acid to 5% sodium chloride solution to make the pH value of the solution drop to about 3, the solution becomes acidic, and the salt mist formed finally turns from neutral salt mist to acid. Its corrosion rate is about 3 times faster than the NSS test.
(3) Copper salt accelerated acetic acid salt spray test (CASS test) is a kind of rapid salt spray corrosion test recently developed 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 approximately 8 times that of the NSS test.
The specific time is converted into:
Neutral salt spray test 24h ⇌ natural environment 1 year
Acetate spray test 24h ⇌ natural environment 3 years
Copper salt accelerated acetic acid salt spray test 24h ⇌ 8 years in natural environment