In order to solve the problem that the atmospheric corrosion test period is too long, a manual accelerated test method can be used to some extent. This method has been widely used at home and abroad. The conditions of various environmental media can be simulated by the artificial accelerated test method. After several days of accelerated test, the results of the natural atmospheric corrosion test equivalent to several years can be obtained. This can judge the atmospheric corrosion resistance of materials or samples in a short period of time, and promote the development of scientific research and the promotion of production applications.
At the same time of adopting the artificial accelerated corrosion test method, not all natural corrosion test methods are abandoned, but they are used at the same time, mutual recognition, mutual verification, and complementarity, so that the artificial accelerated corrosion test method is closer to the result of natural atmospheric corrosion, making it more Reliable, more accurate, and more reliable. Therefore, many units engaged in corrosion research still have a natural corrosion environment test site for testing or assisting the required units for testing.The purpose of the artificial accelerated corrosion test is mainly twofold:
First, the service life of a certain metal material protective film in some atmospheric environments has been known, and the artificial accelerated corrosion test is used to inspect the production unit to manufacture such a material protective film (including conversion film, various coating films, paint films, etc.). When the quality of its manufacturing engineering has met the requirements. In this case, there must be a quality inspection standard level after the test, and a unified evaluation standard should be adopted to ensure its scientific and impartiality.
The second is to determine the corrosion resistance and protective effect of a new material and its protective film in the corresponding atmospheric environment by artificial accelerated corrosion test. In this case, there must be a calculation method for the transformation coefficient of the artificial accelerated corrosion rate and the natural corrosion rate in order to make a reasonable judgment. For example, the corrosion rate of a one-day artificial accelerated corrosion test is approximately equal to the corrosion rate of the natural corrosion test. Moreover, the calculation of such transform coefficients must be accurate and reliable, and can withstand the test and comparison of actual test results.
Commonly used artificial accelerated corrosion test methods are: salt spray test, damp heat test, sulfur dioxide corrosion test, periodic infiltration corrosion test, electrolytic corrosion test, hydrogen sulfide test.
The salt spray test (brine spray test) is one of the main methods for the artificial accelerated corrosion test to test the corrosion resistance of the coating. It simulates rapid corrosion tests on coatings in coastal environmental conditions, mainly to assess coating quality, such as porosity, thickness, requirements, coating surface defects, and quality of pre-painting or post-coating treatment. It is also used to compare the resistance of different coatings to atmospheric corrosion.
According to the composition and conditions of the solution used in the test, the salt spray test is divided into three types: neutral salt spray test (NSS), acetate spray test (ASS) and copper salt accelerated acetate spray test (cASS). method.
The damp heat test is carried out in a damp heat test chamber to simulate the environmental conditions of the coated product in which the temperature and humidity are constant or frequently alternating to cause condensation, and the coating is subjected to a manual accelerated corrosion test. The damp heat test mainly tests the protective properties of various layers, coatings and coatings. Since the corrosion caused by artificially high temperature and high humidity conditions is not very obvious, it is generally not used as a coating quality inspection item alone.
Sulfur dioxide industrial gas corrosion test is a kind of artificial accelerated corrosion test method for coating resistant to industrial atmospheric corrosion. It is mainly used for the evaluation of atmospheric corrosion resistance of various metal film layers, coatings and paint films. The method uses a certain concentration of sulfur dioxide gas to corrode the coating at a certain temperature and relative humidity, and the test results are very close to the actual corrosion of the coating in an industrial atmosphere.
The periodic infiltration corrosion test (referred to as the weekly dip test) is a test method for simulating the rapid corrosion of coatings in semi-industrial marine atmospheres. The results are superior to neutral salt spray in terms of acceleration, simulation and reproducibility. test.
The electrolytic corrosion test (EC test) is a test method for artificial rapid corrosion of anodized coatings on steel parts or zinc die castings.
The hydrogen sulfide test is usually carried out in a test chamber, and is a method of artificially producing an air medium containing hydrogen sulfide to conduct a corrosion test on the coating. Corrosion test only for silver plating or silver plating with a protective layer in an atmospheric medium containing hydrogen sulfide.
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