In-situ Observation of Cosmetic Corrosion Behavior under Atmospheric Environment
Article ID: MT-C2022007
Details
Article ID: MT-C2022007
It is well known that the types of automotive corrosion can be divided into perforation and cosmetic corrosion. Although many studies concerning the mechanism of perforation corrosion have been conducted so far, very few have investigated the mechanism of cosmetic corrosion. In our previous work, the authors found that the initial corrosion behavior in cosmetic corrosion consists of three steps by conducting in-situ observation during a cyclic corrosion test. In the present work, in-situ observation of painted samples with a scratch was performed during an exposure test in Okinawa to examine the cosmetic corrosion behavior under an actual environment. It was found that corrosion started at the moment of salt deposition around the scribed part from air containing salts, and the initial corrosion behavior in the exposure test consisted of three steps, which were the same as in the cyclic corrosion test. In the 1st step, black rust of Fe3O4 formed at the scribed part, and in the 2nd step, under-film corrosion progressed from the scribed part where the black rust had formed. In the 3rd step, the tip of the under-film corrosion displayed swelling behavior. The behavior of each step was also discussed by combining the in-situ observation results with an analysis of environmental factors such as relative humidity and an EPMA analysis.
This Paper was Originally Published in Japanese in Zairyo-to-Kankyo 70 (2021) 18–27. The captions of Figs. 3, 4, 5, 6, 7, 12 and 13 are slightly modified.
