In modern industrial production, many metal materials and their coatings are prone to corrosion during use. To evaluate the corrosion resistance of materials under harsh conditions, salt spray testing (Salt Spray Test) has become a widely used accelerated corrosion testing method. It detects the corrosion resistance of metal materials or coatings by simulating the salt spray environment and is widely used in the fields of automotive, aerospace, electronics, construction, and marine engineering.



One, Basic Principles of Salt Spray Testing



Salt spray testing is an artificial accelerated corrosion test method, with its core being to spray a solution of a certain concentration of sodium chloride (NaCl) on the surface of the sample to form a high humidity and high salt corrosion environment. This environment simulates the corrosion conditions faced by metal materials in coastal areas or industrial pollution areas. During the test, the sample is usually placed in a closed test box with a constant temperature (generally 35℃), and the salt spray is continuously sprayed to accelerate the occurrence of corrosion reactions.



Common salt spray tests include neutral salt spray test (NSS), acetate salt spray test (AASS), and copper accelerated acetate salt spray test (CASS), etc. Different types of tests are suitable for different materials and application scenarios to more truly reflect the corrosion conditions in actual use environments.



Two, Evaluation Indicators of Salt Spray Testing



After the completion of the salt spray test, the evaluation of the corrosion resistance of the sample mainly depends on the following aspects:



1. Corrosion time: The duration from the start of the test to the appearance of corrosion phenomena (such as rusting, bubbling, peeling off, etc.). The longer the time, the better the corrosion resistance of the material.



2. Corrosion degree: Determine the severity of corrosion by observing the corrosion area, depth, and morphology on the surface of the sample, and compare it with the standard rating table.



3. Protective performance: Evaluate the protective effect of coatings or plating in corrosive environments, including whether stripping, bubbling, or cracking phenomena occur.

　　4. Appearance changes: Record the visual changes such as color, luster, and spots of the sample before and after the test as auxiliary evaluation indicators.



Three, Applications and Limitations of Salt Spray Testing

　　Due to its advantages such as simple operation, low cost, and strong repeatability of results, salt spray testing has become an important means for evaluating the corrosion resistance of metals and coatings. For example, in the manufacturing of automobiles, salt spray testing is often used to verify the quality of rust-proof coatings on components; electronic products use this test to evaluate the stability of shell materials in humid salt spray environments.

　　However, salt spray testing also has certain limitations. It is an accelerated test method that can reflect the corrosion resistance of materials in a short period of time, but it cannot be completely equivalent to the long-term corrosion process in natural environments. In addition, different materials have different sensitivities to salt spray, so the test results need to be comprehensively analyzed in combination with the actual use environment.



Four, Conclusion



In general, salt spray testing, as a standard corrosion test method, plays an important role in material research and development, quality control, and product selection. Although it cannot completely replace corrosion testing in natural environments, it can still provide strong support for the evaluation of material corrosion resistance through scientifically designed test plans and reasonable interpretation of test results. With the development of material science and corrosion protection technology, salt spray testing is also continuously optimized and improved, playing a positive role in enhancing product durability and reliability.