Salt fog test

• Salt fog corrosion
  Corrosion is the material or its performance in the role of the environment caused by damage or deterioration. Most of the corrosion occurred in the atmospheric environment, containing oxygen, humidity, temperature and pollutant composition and corrosion factors of atmospheric corrosion. Salt fog corrosion is a common and destructive atmospheric corrosion. Here refers to the chloride salt spray atmosphere, it is the main component of marine corrosion in chloride salt - sodium chloride, it is mainly derived from marine and inland saline areas. Salt fog corrosion on the surface of metal materials is due to the penetration of chloride ion containing the metal surface of the oxide layer and the protective layer and the inner metal occurs due to electrochemical reaction. At the same time, chloride ion containing certain hydration energy, easy to be absorbed instead of oxygen in the chloride layer on the metal surface of the pores and fractures and to exclude, insoluble oxides become soluble chlorides, which become the active surface state of surface passivation. Due to the adverse reaction are very bad.
  
  Salt spray test and Practice
  Salt fog test is a major environmental test using salt spray test equipment to create artificial salt fog environment conditions to test products or metal material corrosion resistance. It is divided into two categories, one kind of exposure test for natural environment, the other is accelerated simulation salt spray test. Artificial simulation of salt spray test is the use of a box of salt fog test equipment has a certain volume of space, artificial methods used in the volume of space, resulting in the salt spray environment to carry out the assessment of product quality of salt spray corrosion resistance. Compared with the natural environment, the salt concentration of chloride salt fog environment, can be several times the general natural environment of salt fog content or a few times, the corrosion speed is greatly improved by salt spray test on the product, the results of the time is greatly shortened. As in the natural exposure environment test of a product sample, the corrosion may be 1, but in the artificial environment of salt fog test, as long as 24 hours, you can get similar results.
  
  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) the neutral salt spray test (NSS test) is an accelerated corrosion test method has wide application areas. It uses sodium chloride salt solution 5%, pH adjustment in the neutral range (6~7) used as a spray solution. The test temperature from 35 DEG C, the requirements of the settlement rate of salt spray between 1 ~ 2ml/80cm -.H.
  (2) acetic acid salt spray test (ASS test) is developed based on neutral salt spray test on. It is to add some acetic acid in 5% Sodium Chloride Solution, the pH value of the solution is reduced to 3 or so, the solution becomes acidic, salt fog formed by neutral salt spray into acid. Its corrosion rate to 3 times faster than 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 of NSS test.
  (4) cyclic salt fog test is a kind of comprehensive salt fog test, it is actually the neutral salt spray test with constant humidity test. It is mainly used for the whole product cavity, through the infiltration moist environment, the salt fog corrosion not only on the surface of the product, also produced inside the product. It is the products of alternate salt spray two kinds of environmental conditions, after the assessment of the whole product electrical properties and mechanical properties have changed.
  
  3、Determination of the salt spray test and test results
  
  4、The standard is unified regulations about repeated things and overview. Salt spray test standard is to salt spray test conditions, such as temperature, humidity, concentration and pH of Sodium Chloride Solution made clear and specific provisions, but also put forward the requirements for the performance test and salt fog box. The same product adopts a salt spray test standard according to the sensitivity characteristics and corrosion rate of metal salt spray test and salt fog of choice. Here are a few salt fog test standards, such as GB/T 2423.17-2008 《basic environmental testing procedures for electric and electronic products - Test Ka: salt fog test method》；GB/T 2423.18-2012《 environmental testing for electric and electronic products part second: Test Kb: salt spray, alternating (Sodium Chloride Solution)》 QB/T 3826-1999 《metal deposits for the light industrial products and chemical treating layers corrosion test method for the determination 》；GB/T 1771-2007《paints and varnishes - Determination of resistance to neutral salt spray》.
  Salt spray test for the purpose of assessing products or metal salt fog corrosion resistance quality, and the results of salt spray test is judged on the quality of the product to determine its verdict, the results are correct and reasonable, is the key to correctly measure the products or metal salt fog corrosion resistance quality. Determination method of salt spray test results: rating method, weighing method, corrosion determining 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 statistical analysis, corrosion, and is not specific for a specific product quality determination.