Galvanized product rust test is not suitable for salt spray test evaluation
Is the hot-dip galvanizing product evaluated by the salt spray test an unsuitable test? What kind of test should the ideal rust test be reasonable? What is the acceptance criteria? If the customer insists that Zhang Guan Li Dai use the salt spray test to meet the acceptance criteria, how long should the plated parts be placed in the general indoor storage environment （constant temperature and humidity environment）, will the salt spray test be more favorable?
The anti-rust test of galvanized products is not suitable for evaluation by salt spray test. Because the galvanized product is in the natural environment, it relies on the stable oxide layer formed on the surface to prevent corrosion, and the salt spray test does not stabilize when the oxide layer is formed. It is constantly destroyed and therefore not suitable for evaluation by salt spray test.
Hot dip galvanized steel surface is not suitable for salt spray test
Hot-dip galvanized steel surface is generally not suitable for salt spray test. When hot-dip galvanized steel is exposed to the atmosphere, zinc carbonate is formed on the surface. Zinc carbonate can effectively protect zinc metal coating and reduce corrosion of zinc metal coating. rate. However, hot dip galvanized steel does not produce zinc carbonate in the salt spray test. Therefore, hot dip galvanized steel generally does not use a salt spray test to evaluate corrosion resistance and service life of different environments. Coatings painted on hot dip galvanized steel surfaces can be tested using the salt spray test method.
Experts on the American Corrosion Doctor website commented on the ASTMB117 salt spray test:
ASTMB117 is the earliest and most widely used salt spray test standard. This standard mainly introduces the sample test piece to be sprayed in a sealed test cabinet at a specific position and angle. The concentration of sodium chloride solution can be 3.5% to 20%. The test cabinet can have a large space design. 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 hot and humid mist through the compressor and the bubble column, and the brine is vaporized by the nozzle into a corrosive salt spray by the gravity supply system. Establish an exposure condition area of 100% relative humidity. For low humidity, forced air is forced through the blower directly through the heater to reach the test cabinet.
US corrosion expert Robert Baboian's question about the evaluation of 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, and in all industries, the salt spray test has very high value in terms of quality control and material properties, such as automotive, aircraft, transportation and infrastructure. The salt spray test is widely used in paint coating systems and is extremely valuable when it is used correctly for comparison of quality control and material properties. For example, ASTMB117 is used for periodic testing in a wide variety of industries, and these tests are extremely valuable because they are closer to actual use. Is Robert Baboian's suspected salt spray test really so good?
Several test problems with ASTMB117 were found when attempting to evaluate the corrosion performance of automotive parts after a salt spray test. Several studies have indicated that ASTMB117 does not provide correct testing of aluminum alloy coatings, or that aluminum-zinc alloy coatings are not expected to be damaged in cold-rolled steel sheets or any other coating similar.