Reasons why the anti-rust test of galvanized products is not suitable for evaluation by salt spray test

　　Whether the salt spray test is used to evaluate whether the hot-dip galvanized product is an unsuitable inspection method? What kind of test should be resorted to for the ideal anti-rust test to be reasonable? What are the acceptance criteria? If the customer insists that Zhang Guanli Dai use the salt spray test as the acceptance standard, how long should the plating part be stored in the general indoor storage environment (constant temperature and humidity environment), which is more beneficial to the salt spray test?

　　The anti-rust strength test of galvanized products is not suitable for evaluation by salt spray test, because galvanized products rely on the stable oxide layer formed on the surface to prevent corrosion in the natural environment, and the salt spray test is indeed when the oxide layer is not stable. , The continuous damage is therefore not suitable for evaluation by salt spray test.

　　The reason why the surface of hot-dip galvanized steel is not suitable for salt spray test

　　The surface of hot-dip galvanized steel is usually not suitable for salt water spray test. When the hot-dip galvanized steel is exposed to the atmosphere, zinc carbonate will be formed on the surface. Zinc carbonate can effectively protect the zinc metal coating and reduce the corrosion of the zinc metal coating. rate. However, hot-dip galvanized steel cannot produce zinc carbonate in the salt spray test. Therefore, the salt spray test is usually not used for hot-dip galvanized steel to evaluate corrosion resistance and service life in different environments. Coatings painted on the surface of hot-dip galvanized steel can be tested using the salt spray test method.

　　Experts from the American Corrosion Doctor website commented on the ASTMB117 salt spray test:

　　ASTMB117 is the earliest and most widely used salt water spray test standard. The standard mainly introduces that the sample test piece is placed in a closed test cabinet at a specific position and angle to undergo a salt water spray test. The concentration of sodium chloride solution can be 3.5% to 20%. The test cabinet can be designed with a large space. Although the salt spray test is widely used in the specification, it is not related to the use characteristics. The hot water is vaporized into a humid mist through the compressor and the bubble tower, and the salt water is vaporized into corrosive salt mist through the nozzle using the gravity supply system. Establish an exposure condition area of ​​100% relative humidity. For low humidity, it is necessary to force the air to pass through the hair dryer directly through the heater to reach the test cabinet.

　　Robert Baboian, an American corrosion expert, questioned the evaluation of the salt spray test

　　When the salt spray test is used correctly, it is one of the most valuable corrosion tests in the world. It has affected all industries. In all walks of life, in terms of quality control and material characteristics comparison, salt water spray test has a very high value. For example, automobiles, airplanes, transportation and infrastructure have industries that apply paint. The salt spray test is widely used in paint coating systems. When it is correctly used for quality control and material characteristics comparison, it is extremely valuable. For example, ASTM B117 is used for periodic tests in a variety of industries. These tests are extremely valuable because they are closer to actual conditions of use. Robert Baboian doubts that the salt spray test is so good?

　　When trying to evaluate the corrosion performance of auto parts after the salt spray test, several test problems of ASTMB117 were found. Several studies have pointed out that ASTM B117 cannot provide correct testing of aluminum alloy coatings, or cannot predict the damage of aluminum-zinc alloy coatings on cold-rolled steel sheets or any other similar coatings.