1. Introduction to Salt Spray Test:

Salt spray corrosion is a common and highly destructive form of atmospheric corrosion.

Salt spray testing is an environmental test that primarily uses artificially simulated salt spray conditions created by salt spray test equipment to evaluate the corrosion resistance of products or metal materials.

Salt spray tests are divided into two main categories: 1. Natural environment exposure tests, 2. Artificially accelerated simulated salt spray environment tests.

The artificially simulated salt spray environment test uses a test equipment called a "salt spray test chamber" to create a salt spray environment within its volume space through artificial methods to evaluate the quality of a product's resistance to salt spray corrosion. Compared to natural environments, the chloride salt concentration in the salt spray environment can be several times or even dozens of times higher than that in natural environments, greatly accelerating the corrosion rate. Conducting salt spray tests on products significantly shortens the time required to obtain results.

2. Classification of Artificially Simulated Salt Spray Tests:

(1) Neutral Salt Spray Test (NSS Test)

This is one of the earliest and most widely used accelerated corrosion test methods. It uses a 5% sodium chloride salt solution with the pH adjusted to the neutral range (6-7) as the spray solution. The test temperature is set at 35°C, and the required salt spray settlement rate is between 1-2 ml/80cm²·h.

(2) Acetic Acid Salt Spray Test (ASS Test)

This test was developed based on the neutral salt spray test. It involves adding a small amount of glacial acetic acid to the 5% sodium chloride solution to lower the pH to around 3, making the solution acidic. The resulting salt spray also becomes acidic. Its corrosion rate is approximately three times faster than that of the NSS test.

(3) Copper-Accelerated Acetic Acid Salt Spray Test (CASS Test)

This is a recently developed rapid salt spray corrosion test abroad. The test temperature is 50°C, and a small amount of copper salt—copper chloride—is added to the salt solution, which strongly induces corrosion. Its corrosion rate is approximately eight times that of the NSS test.

(4) Alternating Salt Spray Test

This is a comprehensive salt spray test that essentially combines a neutral salt spray test with a constant damp heat test. It is primarily used for cavity-type complete products, where moisture penetration causes salt spray corrosion to occur not only on the surface but also inside the product. The test alternates between salt spray and damp heat conditions to evaluate whether the electrical and mechanical properties of the complete product change.