First, the corrosive salt spray corrosion is the material or its performance in the role of the environment arising from the destruction or degeneration.
Most of the corrosion occurred in the atmospheric environment, of the presence of oxygen, humidity, temperature and composition of pollutants such as corrosion and corrosion. Salt spray corrosion is a common and the most destructive atmospheric corrosion. The salt spray mentioned here refers to the atmospheric chloride, which is the main component of marine corrosion in the chloride salt - sodium chloride, which comes mainly from the marine saline-alkali soil and the Mainland Area. Salt spray on the surface of metal materials with corrosion due to the chloride ion penetrating the surface of the metal oxide and protective layer and the internal metal from the electrochemical reaction occurred. At the same time, with a chloride ion hydration can, easily absorbed on the metal surface pores, cracks and replace the chlorination of the exclusion of oxygen, the insoluble oxides into the soluble chloride, a lively surface-passivation Surface. The product of a very bad side effects.
Second, the salt spray test and the actual link
Salt spray test is a major use of salt spray test equipment created by the artificial salt spray environment assessment to products or metal materials resistant to corrosion of the environmental testing. It is divided into two major categories, one for the natural environment exposure test, and the other to speed up the simulation of the environment salt spray test. Artificial salt spray environmental testing is to use a room for a certain volume of test equipment - salt spray proof box, in its volume of space in the artificial methods, resulting in salt spray environment to the products of salt spray corrosion-resistant quality assessment . Compared with the natural environment, the salt spray environment of the chloride concentration, it could be the general content of the natural environment salt spray several times or several times, greatly improving the corrosion rate, the product salt spray test, the results of The time has significantly shortened. If exposed in the natural environment of a product sample for testing, pending corrosion may be one year, and the artificial salt spray test under the condition of the environment, as long as 24 hours, you can get similar results. Artificial salt spray test also includes neutral salt spray test, acetic acid salt spray test, speed up the copper acetate salt spray test, alternating salt spray test.
(1) neutral salt spray test (NSS test) is currently in the first application of the most widely accelerate corrosion of a test method. It uses five percent of the sodium chloride salt solution, the solution for PH value in the neutral range (6-7) used as a spray solution. Test temperature from 35 ℃, salt spray requirements of the settlement in the rate of 1 ~ 2 ml/80cm ². H between.
(2) acetic acid salt spray test (ASS test) is in neutral salt spray test developed on the basis of. It was 5 percent sodium chloride solution to add some acetic acid, so that the solution PH value reduced to about 3, the solution becomes acidic, the final form of salt spray from salt spray have become acidic. The corrosion rate faster than the NSS test three times.
(3) accelerate the copper acetate salt spray test (CASS test) abroad is a newly developed rapid salt spray corrosion test, test temperature for 50 ℃, by adding a small amount of salt solution in the copper - copper chloride, evoked strong corrosion . The corrosion rate is about eight times the NSS test.
(4) alternating salt spray test is a comprehensive salt spray test, it is actually neutral salt spray test pilot and constant hot and humid. It is mainly used in the cavity of thecomplete appliance products, state environmental flows through the infiltration so that the salt spray corrosion not only in the surface of products, products are generated internally. It is the product in the salt spray and hot and humid environment under the conditions of the two alternate conversion, the final assessment complete appliance products, and mechanical properties change there.
Third, the salt spray test standards and test results to determine
The standard outlined by the repetitive things and the unified regulations. Salt spray test standards of salt spray test conditions such as temperature, humidity, and the concentration of sodium chloride solution PH value, and so do the clear and specific provisions, in addition to the salt spray Shiyan Xiang performance by the technical requirements. The same kinds of products that use salt spray test standards according to the characteristics of salt spray test and metal corrosion rate and the degree of sensitivity to salt spray choice. Here are a few salt spray test standards, such as GB/T2423.17-1993 "electrical and electronic products for environmental testing protocols test cards: salt spray test method", GB/T2423.18-2000 "Electrical and Electronic Product Environmental Test Part 2 : Test pilot Kb: salt spray, alternating (NaCl) ", GB5938-86" light industrial products metal plating and chemical treatment of the corrosion resistance test method ", GB/T1771-91" Seqi and varnish in the resistance Determination of salt spray performance. " Salt spray test was aimed at assessing the product or metal materials resistant to salt spray corrosion quality, and the salt spray test results determine the quality of the product is handed down its judgement is correct and reasonable results, is the right measure of salt spray or metal products Corrosion quality of the key. Salt spray test results to determine ways: rating judgement, weighing judgement, a judgement of corrosion, corrosion data statistical analysis. Rating is determined by the corrosion area and the ratio of the total area by a certain percentage of the method is divided into several levels, to a certain level as a basis for passing judgement, it is suitable for flat-panel sample evaluation method is determined by weighing the corrosion test before and after The weight of a sample weighing methods, calculated by the weight of corrosion damage to the sample to judge the quality of corrosion-resistant, it is particularly applicable to a certain corrosion-resistant metal quality assessment; corrosion of a qualitative judgement method is a method to determine , To salt spray corrosion tests, the product is a phenomenon of corrosion on the samples to determine, the general product standards are used in this way; corrosion data statistical analysis designed to provide the corrosion testing, analysis of corrosion data to determine corrosion of confidence data The method, which mainly used for analysis, statistics corrosion, and not specific to a particular judge the quality of products.