Salt Spray Test for Fastener

Salt spray test is an environmental test that mainly uses the artificial simulated salt spray environmental conditions created by salt spray testing equipment to assess the corrosion resistance of products or metal materials. Compared with the natural environment, the salt concentration of chloride in its salt spray environment can be several times or tens of times higher than that in general natural environments, greatly improving the corrosion rate. Conducting salt spray tests on products also greatly shortens the time required to obtain results. The salt spray test methods include: neutral salt spray (NSS) test, acetate spray (ASS) test, copper accelerated acetate spray (CASS) test, etc


Surface treatment is an indispensable part in the manufacturing and use of fasteners. It not only affects the appearance quality of fasteners, but also directly relates to their corrosion resistance and service life. Among the numerous surface treatment requirements, the guarantee of neutral salt spray test is an important indicator. So, what is a neutral salt spray test? What role does it play in the surface treatment of fasteners?


1 Understanding neutral salt spray testing

The neutral salt spray test is an accelerated corrosion test that simulates the corrosion of metal products in marine or humid environments. By spraying a certain concentration of neutral salt solution on the test sample in a specific test chamber, the sample is continuously spray at a certain temperature and humidity, so as to simulate the corrosion conditions that may be encountered in the actual use environment. This test method can effectively evaluate the corrosion resistance of metal products in harsh environments.


2 Requirements for neutral salt spray test 

In the manufacturing process of fasteners, surface treatment usually includes steps such as cleaning, degreasing, phosphating, and spraying. These treatments aim to improve the surface quality of fasteners, enhance their corrosion resistance and aesthetics. However, relying solely on these treatments is not enough to fully ensure the corrosion resistance of fasteners. Therefore, the neutral salt spray test has become an important means to inspect the surface treatment quality of fasteners.

Specifically, the performance of fasteners in neutral salt spray tests should meet certain requirements. Generally speaking, the testing cycle will be determined based on the specific usage environment and requirements of the fasteners. During the test, fasteners should exhibit good corrosion resistance and there should be no obvious rust or corrosion on the surface. Through this experiment, it can be ensured that fasteners can resist the erosion of harsh environments such as moisture and salt spray in actual use, and maintain their good performance and lifespan.


3 Test conditions

The salt solution is prepared with sodium chloride (chemically pure or above) and distilled water, with a concentration of 5 ± 0.1% by weight.

The collected liquid after atomization shall not be reused except for the baffle blocking part.

The pH value of the salt solution before atomization is between 6.5 and 7.2 (35 ℃). When preparing salt solutions, it is allowed to use dilute salt acid or sodium hydroxide aqueous solutions with chemical purity or higher to adjust the pH value, but the concentration must still meet 5 ± 0.1% by weight.

Collect the salt spray deposition of continuous atomization for 16 hours using a funnel with an area of 80 cm ², and the sedimentation rate at any position in the effective space is 1.0~2.0 ml/h 80 cm ²

If standard adopts continuous atomization, and the recommended standard test times are 16, 24, 48, 96, 168, 336, and 672 hours.

During atomization, it is necessary to prevent impurities such as oil stains and dust, as well as the temperature and humidity of the sprayed air from affecting the test conditions of the effective space


4 The importance of neutral salt spray test

The neutral salt spray test is of great significance in the surface treatment of fasteners. Firstly, it can help manufacturers evaluate and improve the surface treatment process of fasteners. By comparing the performance of fasteners under different treatment processes in salt spray tests, manufacturers can identify key factors affecting corrosion resistance, optimize treatment processes, and improve product quality.

Secondly, the neutral salt spray test helps to ensure the reliability of fasteners in practical use. In industries such as marine, chemical, and automotive, fasteners often need to withstand harsh environments such as high humidity and salinity. Through salt spray testing verification, it can be ensured that fasteners have sufficient corrosion resistance in these environments, thereby avoiding performance degradation or failure caused by corrosion.

In addition, neutral salt spray testing can also help improve the market competitiveness of fasteners. In modern industry, product quality and performance are key factors in winning customer trust and market share. Through salt spray testing, manufacturers can demonstrate to customers the advantages of their products in terms of corrosion resistance, thereby improving their market competitiveness.


5 Meet the standard in neutral salt spray testing

To ensure that fasteners meet the standards in neutral salt spray testing, manufacturers need to take a series of measures. Firstly, high-quality raw materials and surface treatment agents should be selected to ensure that the fasteners themselves have good corrosion resistance. Secondly, it is necessary to strictly control the surface treatment process parameters to ensure that each step meets the standard requirements. In addition, it is necessary to strengthen quality inspection and monitoring, and promptly identify and handle possible problems.

Meanwhile, manufacturers should also pay attention to the usage environment and conditions of fasteners. In practical applications, fasteners may be affected by various factors such as temperature, humidity, salinity, etc. Therefore, manufacturers need to develop appropriate surface treatment plans based on specific usage environments and requirements to ensure that fasteners can maintain good corrosion resistance in different environments.


6 Summary

Neutral salt spray test is one of the important means to ensure the surface treatment quality of fasteners. Through the verification of this experiment, it can be ensured that fasteners can resist the erosion of harsh environments and maintain their good performance and lifespan in actual use. Manufacturers should attach importance to the requirements of neutral salt spray testing, continuously optimize surface treatment processes, and improve product quality and market competitiveness. Meanwhile, users should also pay attention to the corrosion resistance of fasteners when using them, ensuring their safety and reliability in specific environments.

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