Salt spray test is a test method commonly used to test the corrosion resistance of materials. In the salt spray test, the test sample is exposed to an aqueous solution containing sodium chloride, so that it is exposed to a high concentration of salt spray for a certain period of time to simulate the corrosion in the real environment. Salt spray tests are commonly used to test the corrosion resistance of materials such as metal materials, coatings and anti-corrosion treatments. The test evaluates the corrosion resistance of the sample in the salt spray environment to judge its corrosion resistance in actual use. Commonly used test standards include ASTM B117, ISO 9227, etc. According to different testing purposes and application requirements, salt spray test can be carried out in different ways.

Salt spray test different test methods and their similarities and differences

Test method
Common salt spray test methods mainly include the following:

NSS test method: NSS refers to neutral salt spray test, using 5% NaCl solution made of neutral salt spray, the test time is usually 48 hours.

AASS test method: AASS refers to acetate spray test, using 0.26% NaCl and 0.5% acetic acid made of acetate spray, the test time is usually 24-48 hours.

CASS test method: CASS refers to copper accelerated acetate spray test, using 0.3% NaCl and 0.3% acetic acid made of copper accelerated acetate spray, the test time is usually 24-48 hours.

SCAB test method: SCAB refers to silver accelerated acetate spray test, using 0.2% NaCl and 0.3% acetic acid made of silver accelerated acetate spray, the test time is usually 24-48 hours.

SWAAT test method: SWAAT refers to the brine acetic acid vapor test, which is made of 3.5% NaCl and 0.25% acetic acid aqueous solution heated and evaporated, and the test time is usually 24 hours.

SWAAT + UV test method: The SWAAT + UV test method is a combination of brine acetic acid vapor test and ultraviolet radiation test to evaluate the corrosion resistance of metal and coating materials under the combined action of multiple environmental factors such as moisture, salt spray and ultraviolet radiation.

PROHESION test method: PROHESION test method is a salt spray test method with a high acceleration effect, using copper to accelerate acetate spray, and constantly changing the test Angle and test time during the test process to simulate different climate and environmental conditions, the test time is usually 1-2 weeks.

Kesternich test method: Kesternich test method is a highly accelerated acid fog test method, using acid fog made of sulfuric acid and water, the test time is usually 1-2 weeks.

Salt spray test different test methods and their similarities and differences

The salt spray test methods listed above are only a few common ones. In fact, there are other different test methods and test parameters, such as test temperature, humidity, air velocity, test Angle and test time, which may affect the test results. Therefore, in the salt spray test, it is necessary to select the appropriate test method and test parameters according to the specific test purpose and application requirements, and ensure the test operation specification and standardization, in order to obtain accurate and reliable test results. Note that different salt spray test methods and standards may have some differences, such as test temperature, humidity, test time, salt spray concentration and other parameters may be different, so in the salt spray test, it is necessary to select the appropriate test methods and standards according to the specific test requirements and application requirements, and test in accordance with the prescribed operating procedures. To avoid too much interference on the accuracy and reliability of the test results.

Salt spray test different test methods and their similarities and differences

NSS, AASS and CASS
NSS, AASS and CASS are three common test methods in salt spray test, and their main differences lie in the preparation of test liquid and test conditions, as follows:

NSS test method: NSS is the abbreviation of neutral salt spray test. Neutral salt spray made of 5% NaCl solution is used for the test, and the test time is 48 hours. The NSS test method is suitable for testing the corrosion resistance of general metal materials and coatings, such as steel, aluminum, zinc, copper, etc.

AASS test method: AASS is the abbreviation of acetate spray test, using 0.5% acetic acid and 0.26% NaCl solution made of acetate spray test, the test time is 24~48 hours. AASS test method is suitable for testing the corrosion resistance of coating and surface treatment, such as electroplating, anodizing, etc.

CASS test method: CASS is the abbreviation of copper accelerated acetate spray test. Copper accelerated acetate spray made of 0.3% acetic acid and 0.3% NaCl solution was used for the test, and the test time was 24 to 48 hours. CASS test method is suitable for testing the corrosion resistance of coating and surface treatment, such as electroplating, anodic oxidation, etc. Compared with NSS and AASS test methods, CASS test method has more acceleration and accuracy.

In addition to the preparation of the test solution and the test time, there are some other differences between NSS, AASS and CASS, including the following:

The pH value is different: the salt spray used in the NSS test method is neutral, and the pH value is about 6.57.2; The salt spray used in the AASS test method is acidic, with a pH value of about 3.13.3; The salt spray used in the CASS test method is neutral, with a pH value of about 6.5 to 7.2.

Different test results: NSS, AASS and CASS test methods also have certain differences in test results due to different test fluids. Under normal circumstances, CASS test method is more accelerated and accurate, and can detect the corrosion and durability of coatings and metal materials faster. The AASS test method is more rigorous and demanding, which can better simulate the corrosion in the actual environment.

Salt spray test different test methods and their similarities and differences

Different test equipment and operating methods: Although NSS, AASS and CASS test methods are all salt spray tests, their test equipment and operating methods may be different. For example, CASS test methods require the use of copper accelerators, while NSS and AASS do not; CASS test method requires recycling and filtration of test salt spray, while NSS and AASS do not have this requirement.

Different scope of application: The NSS, AASS and CASS test methods also have some differences in the types of materials and coatings applicable. In general, the NSS test method is suitable for testing the corrosion resistance of general metal materials and coatings, such as steel, aluminum, zinc, copper, etc. AASS test method is suitable for testing corrosion resistance of coating and surface treatment, such as electroplating, anodic oxidation, etc. The CASS test method has a wider range of applications, not only for testing the corrosion resistance of coatings and metal materials, but also for testing the durability and quality assessment of various chemical treatments and surface treatment methods.

Different economy and environmental protection: Due to the different test fluids, NSS, AASS and CASS test methods also have certain differences in terms of economy and environmental protection. In general, NSS test method is one of the lowest cost and most widely used salt spray test methods, while AASS and CASS test methods are more demanding and precise than NSS, and the test cost and liquid handling cost are correspondingly higher. At the same time, CASS test method requires the use of copper accelerator, so there may be some problems in environmental protection.

Different test time: The test time of NSS, AASS and CASS test methods is also different. Under normal circumstances, the test time of NSS test method is 48 hours; The test time of AASS test method is 2448 hours. The test time of CASS test method was 2448 hours. Due to the different test time, there are some differences in the test results and acceleration effect of the three test methods.

Different simulated environments: NSS, AASS and CASS test methods also have certain differences in simulated environments and corrosion conditions. In general, the NSS test method mainly simulates the Marine environment and the snowmelt salt in winter area. The AASS test method mainly simulates the road salt on the motorway. CASS test method mainly simulates environmental conditions such as industrial environment, cooling water, electronic appliances and so on.

Salt spray test different test methods and their similarities and differences

Different detection methods: NSS, AASS and CASS test methods also have certain differences in detection methods. In general, NSS test methods mainly include visual examination, microscope examination, quality assessment and weight change. AASS test method mainly includes visual examination, microscope examination, thickness change, color change, red rust and white rust detection index. CASS test mainly includes visual examination, microscope examination, thickness change, copper ion deposition and red rust detection indexes.

Different test temperatures: NSS, AASS and CASS test methods also have some differences in test temperatures. Under normal circumstances, the test temperature of NSS test method is 35℃. The test temperature of AASS test method is 50℃. The test temperature of CASS test method is 50℃. Due to the difference of test temperature, the three test methods also have some differences in simulating the actual environment and accelerating effect.

Different test equipment: NSS, AASS and CASS test methods also have certain differences in test equipment and equipment. Under normal circumstances, the NSS test method requires the use of independent salt spray test chamber or corrosion test cabinet and other equipment; AASS test method requires the use of special corrosion test cabinet and automatic sprayer equipment; The CASS test method requires the use of corrosion test cabinets with copper accelerators and automatic sprayers.

Different test standards: NSS, AASS and CASS test methods also have certain differences in test standards and evaluation methods. In general, NSS test methods are usually evaluated using ASTM B117 standards; AASS test methods were evaluated using ASTM B368 or JIS H 8502. The CASS test method was evaluated using ISO 9227.

Salt spray test different test methods and their similarities and differences

All in all, NSS, AASS and CASS test methods are common methods in salt spray test, and their main differences lie in the preparation of test liquid and test time. According to different test purposes and application requirements, it is necessary to select appropriate test methods and standards, and carry out tests in strict accordance with the prescribed operating procedures to obtain accurate and reliable test results. In addition to the preparation of test solution and test time, there are other differences between NSS, AASS and CASS test methods, including test results, pH value, test equipment and operation methods. When selecting the appropriate test method, it is necessary to consider these factors according to the specific test requirements and application requirements, and select the appropriate test method and standard, so as to avoid too much interference on the accuracy and reliability of the test results. Different test methods may adopt different standards and evaluation methods for testing and evaluation. It is necessary to select appropriate standards and methods according to specific test requirements and application requirements, and carry out testing and evaluation in strict accordance with the prescribed operating procedures. At the same time, in the salt spray test, it is also necessary to pay attention to the control and adjustment of the test conditions and test environment, so as not to bring too much interference to the accuracy and reliability of the test results. NSS, AASS and CASS test methods have some differences in test time, simulated environment and acceleration effect, but these differences do not mean that one method is better or worse than the other. When selecting the test method, it is necessary to select the more appropriate method according to the actual needs and specific conditions, and test in strict accordance with the specified test standards and operating procedures, so as to avoid excessive interference on the accuracy and reliability of the test results.