Salt spray test is a kind of environmental test that mainly uses artificial simulated salt spray environmental conditions created by salt spray test equipment to evaluate the corrosion resistance of products or metal materials.
Its purpose is to assess the salt spray corrosion resistance quality of products or metal materials, and the salt spray test results judgment is the judgment of product quality, its judgment results are correct and reasonable, is the key to correctly measure the salt spray corrosion resistance quality of products or metals.
The technical indicators of salt spray test include: salt solution concentration, relative humidity, temperature, salt spray time, storage time, test period, fog collection amount, PH value.
Type of salt spray test
The neutral salt spray test (NSS test) is the earliest application of the most widely used accelerated corrosion test method. It uses 5% sodium chloride solution in solution PH as a spray solution adjusted to the neutral range (6 to 7). The test temperature was 35 ° C, and the salt spray precipitation rate was required to be 1 to 2ml / 80cm·h.
Acetic acid spray test (ASS test) is based on the development of neutral salt spray test. By adding some glacial acetic acid in 5% sodium chloride solution, the PH is reduced to about 3, the solution becomes acidic, and finally the salt spray is formed from the neutral salt spray, forming the acid. Its corrosion rate is about 3 times faster than the NSS test.
The copper salt Accelerated acetate test (CASS test) is a newly developed rapid salt spray corrosion test. The test temperature is 50℃, and a small amount of copper salt-copper chloride is added to the salt solution, which causes severe corrosion. The corrosion rate is about eight times that of the NSS test.
The alternating salt spray test is a comprehensive salt spray test, which is actually a neutral salt spray test plus a constant wet and heat test. It is mainly used in cavity mechanical products, through the penetration of tidal environment, so that salt spray not only corrodes on the surface of the product, but also inside the product. It is the product in salt spray and wet two in the alternate conversion of environmental conditions, the electrical performance of the entire product and the final evaluation of mechanical properties have changed.
The effect of salt spray test is not the same for products that have been surface treated and products that have not been surface treated
Products that have not been surface treated
In the current stainless steel fasteners, without any surface treatment, the salt spray test time of stainless steel screws is 48 hours, and the nut is 96 hours. However, affected by the surface roughness of the product itself, the possibility of rust is not ruled out before 48 hours.
Surface treated products
After surface treatment, the salt spray test time can reach 1000 hours for general products (except carriage bolts), and the flat elastic pad can reach 500 hours. The actual situation is greatly affected by the surface roughness of the product itself.
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