The corrosion of steel samples with protective coatings subjected to natural and accelerated weathering was investigated by the means of digital image analysis. Automotive steel 08u (DC04 according to EN 10130) with and without hot-dip galvanization (DX54 according to EN 10346) was used for the testing. All samples were coated with the cataphoretic primer and coatings were scratched according to GOST 9.401, Method B (EN ISO 9227:2012). Part of the samples was exposed to the temperate maritime atmosphere of the Akimov Gelendzhik Climatic Testing Center: a branch of the All-Russian Scientific Research Institute of Aviation Materials. Some of the samples which were exposed outside were subjected to salt spray every 24 hours. Corrosivity of the atmosphere in the area of the testing is classified as C3 according to ISO 9223. Also, the part of samples was subjected to the accelerated cyclic corrosion test according to VDA 621-415. For all the samples, the corrosion creep from scratches was measured according to GOST 9.401 and digital image analysis was applied. The edges of the corrosion creep were detected using a few algorithms: by fitting the colors' intensity profiles and by calculating the derivative of the colors' intensity profiles. The main characteristics analysed were corrosion creep from the scratches and the corrosion defects. The distributions of the measured characteristics were used to evaluate their basic statistic parameters: mean value, standard deviation and shape parameters. Digital image analysis may be used to obtain statistical parameters of corrosion, such as the distributions of the corrosion creep from the scratch, shape and area of corrosion products. The research results were used to quantitatively describe corrosion creep from the scratch on the coated samples which were exposed to a harsh environment of maritime atmosphere, salt spray, and cyclic corrosion tests.
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