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Second, the salt spray test and the actual ( BE-CS series salt spray test machine)
The salt spray test is an environmental test that uses artificial simulated salt spray environmental conditions created by salt spray test equipment to evaluate the corrosion resistance of products or metal materials. It is divided into two categories, one is the natural environmental exposure test, and the other is the artificial accelerated simulated salt spray environment test. The artificial simulated salt spray environment test uses a test equipment with a certain volume space —the salt spray test chamber , to artificially use the salt spray environment in the volume space to assess the salt spray corrosion resistance quality of the product. . Compared with the natural environment, the salt concentration of the chloride in the salt spray environment can be several times or several times higher than the salt spray content of the general natural environment, so that the corrosion rate is greatly improved, and the product is subjected to a salt spray test to obtain a result. The time is also greatly shortened. If a product sample is tested in a natural exposure environment, it may take 1 year to corrode , and in a simulated simulated salt spray environment, as long as 24 hours, similar results can be obtained.
The artificial simulated salt spray test includes a neutral salt spray test , an acetate spray test, a copper salt accelerated acetate spray test, and an alternating salt spray test.
1. Neutral salt spray test ( NSS test) is an accelerated corrosion test method that appears in the current application field of Zui. It uses a 5% aqueous solution of sodium chloride solution, and the pH of the solution is adjusted to a neutral range ( 6 to 7 ) as a solution for spraying. The test temperature is taken at 35 °C , and the sedimentation rate of salt spray is required to be between 1 and 2 ml/80 cm2.h.
2. The acetate spray test ( ASS test) was developed on the basis of the 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 salt spray formed after the Zui also becomes acidic from the neutral salt spray. Its corrosion rate is about 3 times faster than the NSS test .
3 , copper salt accelerated acetate spray test ( CASS test) is a rapid development of a rapid salt spray corrosion test abroad, the test temperature is 50 ° C , a small amount of copper salt - copper chloride added to the salt solution , strongly induced corrosion. Its corrosion rate is about 8 times that of the NSS test .
4 Alternating salt spray test is a comprehensive 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 penetration of the tidal environment, salt spray corrosion is generated not only on the surface of the product but also inside the product. It converts the product alternately under the two conditions of salt spray and damp heat. After the test, the electrical and mechanical properties of the whole product are checked.
3. Determination of salt spray test standards and test results
Standards are uniform rules for repetitive things and summaries. The salt spray test standard specifies the salt spray test conditions, such as temperature, humidity, sodium chloride solution concentration and pH value, and also sets technical requirements for the performance of the salt spray test chamber. The salt spray test standard for the same product is selected according to the characteristics of the salt spray test, the corrosion rate of the metal, and the sensitivity to salt spray. Here are a few standard salt spray test, such as GB / T2423.17-1993 "electric and electronic products environmental testing procedures Test Ka: Salt mist", GB / T2423.18-2000 "Environmental testing electric and electronic products - Part 2 : Test Test Kb : Salt Spray, Alternating (Sodium Chloride Solution), GB5938-86 "Test Method for Corrosion Resistance of Metal Coatings and Chemical Treatment Layers of Light Industrial Products", GB/T1771-91 " Resistance of Paints and Varnishes" Determination of salt spray performance.
The purpose of the salt spray test is to assess the salt spray corrosion quality of products or metal materials. The salt spray test results are judged on the quality of the product. The judgment result is correct and reasonable. It is a correct measure of the product or metal salt spray resistance. The key to corrosion quality. The methods for determining the salt spray test results include: rating determination method, weighing determination method, corrosion occurrence determination method, and corrosion data statistical analysis method. The rating determination method divides the percentage of the ratio of the corrosion area to the total area into several levels according to a certain method, and uses one level as the basis for the qualification judgment, which is suitable for the evaluation of the flat sample;
Brief introduction of basic knowledge and practical situation of salt spray test chamber
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Our company specializes in producing BE-CS series salt spray test chambers. The following are the test standards and brief introductions of salt spray test chambers :
1. Corrosion is the destruction or deterioration of a material or its properties caused by the environment. Most of the corrosion occurs in the atmosphere, which contains corrosive components and corrosive factors such as oxygen, humidity, temperature changes, and pollutants. Salt spray corrosion is a common and devastating atmospheric corrosion. Mentioned here refers to salt spray atmosphere chloride, its main ingredient is corrosive ocean chloride salt - sodium chloride, it is mainly from marine and inland saline areas. The corrosion of the surface of the metal material by the salt spray is caused by the electrochemical reaction between the oxide layer containing the chloride ions penetrating the metal surface and the protective layer and the internal metal. At the same time, chloride ions contain a certain hydration energy, which is easily adsorbed on the pores of the metal surface, and the cracks are displaced and replace the oxygen in the chlorinated layer, turning the insoluble oxide into a soluble chloride, making the passivated surface active. surface. Causes a bad reaction to the product.
The weighing determination method is to evaluate the corrosion resistance quality of the sample by calculating the weight of the corrosion loss by weighing the weight of the sample before and after the corrosion test. It is especially suitable for assessing the corrosion resistance quality of a certain metal;
The corrosion occurrence determination method is a qualitative determination method, which determines the sample after the salt spray corrosion test, whether the product is corroded or not, and most of the general product standards adopt this method;
The statistical analysis method of corrosion data provides a method for designing corrosion tests, analyzing corrosion data, and determining the confidence of corrosion data. It is mainly used for analysis and statistical corrosion, rather than for specific quality determination of a specific product.
The salt spray test has three kinds of neutral salt spray test N SS , acetate spray AA SS and copper accelerated acetate spray CA SS , also known as copper chloride acetate spray test , in which the application of Zui Guang is neutral salt. Fog test. The basic content of the salt spray test is a 5% sodium chloride aqueous solution sprayed in a test chamber at 35 degrees Celsius to simulate an accelerated corrosion method in a seawater environment. The length of the tolerance time determines the corrosion resistance. Salt spray tank volume of not less than 012 m 3, zui really less than 014 m3, inside temperature 35 ℃ ± 2 ℃, spray pressure of 70 ~ 170kPa, at least two salt spray collector, collecting area of 80 cm 2. Each of the test surface 15 to 30° in the vertical direction, the salt spray can be freely settled on the measured surface, can not be directly sprayed, the test bracket is made of glass, plastic, and the test pieces can not touch each other and drip with each other ; the temperature inside the box is 35 °C ± 2 °C , each Collector collection solution 1 ~ 2 mL ö h.