Release time：2020-01-16 18:44 Browse：
In the in-depth discussion of extension screws, especially outer hexagonal long screws in the Neutral Salt Spray Test performance and test duration, we first need to understand the basic concept of neutral salt spray test (NSS) and its purpose. This test method is widely used to evaluate the corrosion resistance of metal materials and their protective layers (such as electroplating, spraying, etc.) under specific environmental conditions. For fasteners such as outer hexagonal long screws, their corrosion resistance is directly related to the service life and safety of the product, so the neutral salt spray test is particularly important.
Basic principles of neutral salt spray testing
Neutral salt spray testing is to evaluate the corrosion resistance of the sample by simulating the corrosive environment of the Marine environment or salty atmosphere, exposing the sample to be tested to a continuous spray formed by sodium chloride (NaCl) solution to accelerate the corrosion process. The test environment is usually kept within the neutral pH range (about 6.5 to 7.2) and the temperature is controlled within a certain range (usually 35°C±2°C) to simulate the environmental conditions in actual use.
Lengthening screws and neutral salt spray test
For extension screws, especially outer hexagonal long screws, due to their complex structure, large surface area, and often used as connectors, they are more susceptible to corrosion in harsh environments. Therefore, when conducting neutral salt spray testing, special attention needs to be paid to the following points:
1. Sample preparation: Before the test, ensure that the screw surface is clean and free of oil and other impurities, and pre-treatment in strict accordance with the standard provisions, such as oil removal, cleaning, drying, etc., to ensure the accuracy of the test results.
2. Test conditions setting: according to the specific requirements of the product and standard specifications, set the appropriate salt spray concentration, spray rate, test chamber temperature and humidity and other parameters. For most metal materials, the standard cycle of neutral salt spray testing usually ranges from 24 hours to thousands of hours, depending on the expected service life and corrosion resistance requirements of the product.
3. Observation and record: During the test process, it is necessary to regularly observe the changes of the screw surface, and record the time point and degree of white rust, red rust or other corrosion phenomena. White rust, that is, the formation of white or gray corrosion products on the surface, is a common initial corrosion of metals in salt spray environments. The time and speed of its appearance can reflect the corrosion resistance of the screw.
When is white rust normal?
There is actually no fixed answer to the question of "when white rust is normal", because it depends on a number of factors, including but not limited to the type of material, the quality of the surface treatment, the severity of the test conditions, and the expected service life of the product. In general, if in the neutral salt spray test of the outer hexagonal long screw, there is obvious white rust in a short time (such as within a few hours), it is likely to mean that the corrosion resistance of the screw is poor, and the material or surface treatment process needs to be improved. On the contrary, if there is slight white rust after a long time of testing (such as hundreds or even thousands of hours), it means that the screw has good corrosion resistance.
However, it is important to note that even the appearance of white rust does not mean that the screw has completely failed. In practical applications, the corrosion process is often a gradual process, and white rust is only a manifestation of the initial corrosion. Therefore, when evaluating the corrosion resistance of screws, in addition to observing the occurrence time of white rust, other factors need to be considered comprehensively, such as the depth of corrosion, the expansion speed and the impact on the performance of screws.
conclusion
In summary, among the extension screws, the test time of the outer hexagonal long screws in the neutral salt spray test and the time of white rust are all important indicators to evaluate their corrosion resistance. However, the specific test duration and the normal time range for the appearance of white rust need to be determined according to the specific requirements and standard specifications of the product. In order to ensure the accuracy and reliability of the test results, it is recommended to fully understand the characteristics of the product, the expected use environment and relevant standards and specifications before the test, and to prepare the sample, set the test conditions and analyze the results in strict accordance with the requirements. At the same time, through continuous technical improvement and innovation, improve the corrosion resistance of screws to meet the increasingly demanding market demand.
