Salt spray test results how to see

First, understanding of salt fog:

Corrosion is the destruction or deterioration of a material or its properties caused by the action of the environment. Most of the corrosion occurs in the atmosphere. The atmosphere contains oxygen, humidity, temperature changes, and contaminants such as corrosion and corrosion factors. Salt spray corrosion is a common and most damaging atmospheric corrosion. The salt spray here refers to the chloride atmosphere, and its main corrosion component is the chloride salt in the ocean, nacl, which is mainly derived from the sea and saline areas in the interior. The corrosion of the surface of the metal material by the salt spray is caused by the electrochemical reaction between the contained chloride ions penetrating the metal surface oxide layer and the protective layer and the internal metal. At the same time, the chloride ion contains a certain amount of hydration energy, which is easily adsorbed on the pores and cracks on the metal surface to displace and replace the oxygen in the chloride layer, transforming the insoluble oxide into soluble chloride, and making the passive state surface become lively. surface. Caused a very bad adverse reaction to the product.
Second, the salt spray test and the actual link:

The salt spray test is an environmental test that mainly uses the simulated salt spray environmental conditions created by salt spray test equipment to assess the corrosion resistance of a product or metal material. It is divided into two major categories, one for natural environmental exposure tests and the other for accelerated artificial salt spray environmental tests. Artificially simulated salt spray environmental test is to use a test equipment with a certain volume of space - salt spray test chamber, in its volumetric space with artificial methods, resulting in salt spray environment to assess the product's resistance to salt spray corrosion quality and quality . Compared with the natural environment, the salt concentration of the chloride in the salt spray environment can be several times or several times of that of the normal natural environment, which greatly increases the corrosion rate. The salt spray test is performed on the product and results are obtained. The time has also been greatly shortened. If a product sample is tested under natural exposure conditions, the corrosion may take one year. However, if the test is performed under simulated artificial salt spray conditions, similar results can be obtained as long as 24 hours.

Artificially simulated salt spray tests include 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 currently applied fields of accelerated corrosion test methods. It uses a 5% nacl salt solution and the pH of the solution is adjusted to a neutral range (6 to 7) as a spray solution. The test temperature is taken at 35°C, and the deposition rate of salt spray is required to be between 1 and 2ml/80cm2.h.

(2) Acetate spray test (ASS test) was developed based on the neutral salt spray test. It is to add some glacial acetic acid in the 5% nacl solution, so that the PH value of the solution is reduced to about 3.0-3.2, the solution becomes acidic, and the final salt fog is also changed from neutral salt fog to acidic. Its corrosion rate is about three times faster than the NSS test.

(3) Accelerated Acetate Salt Spray Test (CASS test) is a rapid salt spray corrosion test recently developed abroad. The test temperature is 50°C. A small amount (0.26 g/1 litre of salt water) is added to the salt solution. Induced corrosion. Its corrosion rate is about 8 times that of the NSS test.

(4) The alternating salt spray test is an integrated salt spray test, which is actually a neutral salt spray test plus a constant damp heat test. It is mainly used for cavity type machine products. Through the infiltration of the tide environment, the salt spray corrosion will not only be produced on the surface of the product, but also produced inside the product. It is to switch the product alternately under the conditions of salt spray and damp heat, and finally to assess whether there is any change in the electrical and mechanical properties of the complete product.
Third, the salt spray test results are:

Rating determination method, weighing determination method, corrosive appearance determination method, and corrosion data statistical analysis method.

The rating judgment method divides the percentage of the ratio of the erosion area to the total area into several levels according to a certain method, and uses a certain level as a criterion for the determination of conformity. It is suitable for flat plate samples for evaluation; the weighing determination method passes through before and after the corrosion test. The weight of the sample is weighed, and the weight lost from the corrosion is calculated to evaluate the quality of the corrosion resistance of the sample. It is particularly suitable for assessing the corrosion resistance of a certain metal; the corrosive matter occurrence determination method is a qualitative determination. The method, which is based on the salt spray corrosion test, determines whether the product is corroded to determine the sample. Most of the general product standards use this method. The corrosion data statistical analysis method provides confidence in the design of corrosion tests, analysis of corrosion data, and determination of corrosion data. Degree method, which is mainly used for analysis and statistics of corrosion, not for the specific quality determination of a specific product.

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