Anticorrosive Coating Corrosion and Aging Performance Test Method
November 12, 2020
Anticorrosive coatings are widely used in emerging marine engineering, modern transportation, energy industry, large industrial enterprises and municipal facilities. More and more attention is paid to its corrosion and aging properties. The anti corrosion performance of the coating directly affects the service life and safety of the project.
■ The history of research on corrosion and aging performance of anticorrosive coatings is very long, but generally there are:
1) In the laboratory accelerated test, the salt spray corrosion test, the xenon lamp aging test, and the ultraviolet aging test are generally independent of each other. The accelerated test is rarely combined with salt spray and light conditions, and the salt spray test is mostly continuous neutral salt. Mainly in fog conditions;
2) Most manufacturers mainly rely on accelerated laboratory tests and rarely conduct outdoor natural corrosion exposure. Even if outdoor natural corrosion projects are carried out, they are rarely able to compare atmospheric data with laboratory results to verify whether laboratory tests can Reproduce the corrosion and aging conditions of the product under real outdoor use conditions.
■ Laboratory accelerated salt spray test methods
1. Continuous neutral salt spray test
ASTMB117 is still one of the main standards for salt spray corrosion testing, requiring samples to be continuously exposed to 5% salt spray at 35°C.
2. Circulating salt spray test
The cyclic corrosion test is a salt spray test that is more realistic than the traditional constant exposure. Because most products are actually exposed outdoors in a dry and wet alternate environment, simulating natural and periodic conditions, the laboratory accelerated testing will be more relevant. Studies have shown that after cyclic corrosion testing, the relative corrosion rate, structure, and morphology of the samples are very similar to outdoor corrosion results. Therefore, the cyclic corrosion test is closer to real outdoor exposure than the continuous neutral salt spray method. This method is widely used in the automotive industry.
3. Corrosion + aging cycle
For some coatings, increasing UV exposure during the corrosion cycle can improve the test relevance of some products. This is because ultraviolet rays damage the paint and reduce the protection of the paint on the metal substrate, making the product more prone to corrosion.
The ASTMD5894 standard is also a cyclic corrosion + aging test method