What is the salt spray test?Let’s talk about the determination of salt spray test standard and test results.
Salt spray test is a kind of environmental test to evaluate the corrosion resistance of products or metal materials by artificial simulated salt fog environment created by salt fog test equipment. It is divided into two categories, one is natural environmental exposure test, and the other is artificial accelerated simulation of salt spray environmental test. Artificial simulated salt fog environmental test is to use a certain volume of space test equipment salt fog test box, in its volume space with artificial methods, resulting in salt fog environment to product salt fog corrosion performance quality assessment. Compared with the natural environment, the salt concentration of chloride in the salt fog environment can be several times or several times as much as that of the common natural environment. The corrosion rate is greatly improved, and the salt spray test of the product is carried out, and the time for the result is greatly shortened. If a product sample is tested in a natural exposure environment, it may take 1 years for the corrosion of the product, and the similar results can be obtained as long as 24 hours under the artificial simulated salt fog environment. Artificial simulation of salt spray test and neutral salt spray test, salt spray test, copper accelerated acetic acid salt spray test, cyclic salt fog test.
(1)neutral salt spray test (NSS test) is the earliest method of accelerated corrosion test, which is the most widely used field at present. It uses 5% saline solution, pH value in neutral range (6~7) as spray solution. The test temperature is 35 degrees, and the sedimentation rate of salt fog is between 1 and 2ml/80cm2.h.
(2)acetic acid salt spray test (ASS test) is developed based on neutral salt spray test on. It is added glacial acetic acid in 5% brine solution, the pH value of the solution is reduced to about 3, the solution becomes acidic, and finally the salt fog is changed from neutral salt fog to acid. Its corrosion rate is about 3 times faster than that of NSS test.
(3)copper accelerated acetic acid salt spray test (CASS test) is a kind of rapid salt fog corrosion test abroad newly developed test, the temperature is 50 DEG C, adding a small amount of copper salt and copper salt solution, strongly induced corrosion. Its corrosion rate is about 8 times that of the NSS test.
(4)alternating salt spray test is a comprehensive salt spray test. It is actually a neutral salt spray test plus constant damp heat test. It is mainly used in the cavity type of the whole product, through the infiltration of the tide environment, so that salt fog corrosion not only in the product surface, but also in the production of the internal products. It converts the product into two environments, namely salt fog and wet heat, and finally checks whether the electrical performance and mechanical properties of the whole product have changed.
Salt fog test standards and determination of test results:
Standards are the uniform rules for repetitive things and overviews. The standard of salt fog test is the specific specification of salt fog test conditions, such as temperature, humidity, salt solution concentration and pH value, etc., and also puts forward technical requirements for the performance of salt fog test box. The standard of salt spray test for the same product should be chosen according to the characteristics of salt spray test, the corrosion rate of metal and the sensitivity of salt fog. Here are a few salt fog test standards, such as GB/T2423.17 - 1993 "basic environmental testing procedures for electric and electronic products - Test Ka: salt fog test method", GB/T2423.18 2000 "environmental testing for electric and electronic products part second: Test Kb: salt spray, alternating (saline solution)", GB5938 86 "metal deposits for the light industrial products and the chemical processing layer corrosion test method", GB/T1771 91 "neutral salt spray resistance of paints and varnishes - Determination of".
The purpose of salt spray test is to evaluate the quality of salt fog corrosion resistance of products or metal materials, and the judgment of salt fog test results is the judgment of product quality. Whether the judgment result is correct or not is the key to correctly measure the corrosion resistance of products or metals. The judgment methods of salt fog test results are: rating method, weighing method, corrosion occurrence judgment method, corrosion data statistical analysis method. The rating decision is the percentage of corrosion area and total area ratio according to certain method is divided into several levels, as a basis to determine the qualified level, it is suitable for flat sample evaluation; weighing judgment method is through the method of heavy corrosion test samples before and after weight, calculate the corrosion loss the weight of sample quality evaluation of corrosion resistance, it is suitable for assessment on corrosion resistance of a metal corrosion quality; determining method is a qualitative judgement method, it takes the salt fog corrosion test, whether the product is produced to determine the corrosion phenomenon on samples, this method mostly adopts the general product standard; the corrosion data statistical analysis method provides the design of corrosion test, analysis method to determine the degree of confidence of corrosion data of corrosion data, it is mainly used for analysis and statistics The corrosion condition, not the quality judgment of a specific product.