Salt spray corrosion is a common marine atmospheric corrosion, its main corrosive component is sodium chloride, and its damage area mainly occurs in coastal areas. Salt spray test is an environmental test that mainly uses the artificial simulation of salt spray environmental conditions created by salt spray test equipment to assess the corrosion resistance of products or materials. Neutral salt spray test is divided into neutral salt spray test, acetic acid salt spray test and copper accelerated acetic acid salt spray test. Among them, the neutral salt spray is the most widely applicable, and can be used to assess the corrosion resistance of various inorganic or organic coating products. Acetic acid salt spray and copper accelerated acetic acid salt spray is applicable to copper + nickel + chromium or nickel + chromium decorative plating, also applicable to aluminum anodic conversion film.
I. Standard of neutral salt spray test
The standard is a unified regulation made for repeatable things and overview. Neutral salt spray test standard is the salt spray test conditions, such as temperature and humidity, sodium chloride solution concentration, pH and other clear and specific provisions; in addition to the salt spray test chamber performance to put forward technical requirements.
2. Neutral salt spray test standard differences
Neutral salt spray test using 5% sodium chloride salt solution, i.e., pH adjustment in the neutral range as a solution for spraying. Test temperature are taken 35 ℃, salt spray deposition rate in 1 ~ 2mL / 80cm2 - h between. At present, different countries, industries, manufacturers of salt spray test is not exactly the same, the formation of a lot of salt spray test standards.
Salt spray test requires the use of sodium chloride solution as a corrosive medium, so the sodium chloride solution used to meet certain requirements, when using chemically pure or above sodium chloride and deionized water, all standards meet the requirements. However, when measuring the pH of the solution, it must be measured at 35℃, which increases the difficulty of pH measurement.
Test the salt spray temperature and the amount of salt spray deposition rate, the corrosion effect of the test has a great impact, so the standard are specified in the test temperature and salt spray deposition rate. The spray pressure affects the salt solution collection rate, in addition to the placement angle of the specimen on the salt spray corrosion test also has a certain impact. Different standards also have differences in operational requirements.
Specimen inspection and test time
Salt spray test are required to test without external interference, after the end of the test to remove the test solution residue on the surface of the sample after drying, to facilitate the determination of the test results, evaluation criteria affect the direct determination of the test results, in addition to the test time also determines the level of corrosion resistance of the product needs to achieve. Test open box inspection requires as little time and times as possible; after the test rinse with water, remove the test solution residue on the surface of the specimen after drying, the use of different determination methods may appear different test results.
Strict control of the salt spray test process is the key to providing test re-ability. A global, basic artificial accelerated corrosion test standard, the adoption of which is more in line with the trend of economic globalization. The standard from the test water, reagents, salt solution concentration, solution pH, sample placement angle, test chamber performance requirements, as well as the sample handling before and after the test are given detailed, scientific and operational requirements. It is recommended that laboratory personnel in the development of neutral salt spray test operation specifications, using the standard requirements for the development of the use of their own protocols.