| As the organic coating has widely used, the corrosion of the complex atmospheric environment would inevitablely occur and cause great harm. If we can make more comprehensive and accurate evaluation to the failure of organic coatings and know the failure mechanism, then take effective measures, which can reduce the occurrence and development of corrosion damage. Based on the above problems, it is particularly important to reaseach the failure of organic coatings protection system and provide an important basis for making measures the relevant standards to prevent corrosion.This paper carried out research on the failure of organic coatings protection system in simulated marine atmospheric atmosphere accelerated corrosion. First, established an integrated comprehensive model by means of Analytic Hierarchy Process (AHP). Second, verified the model by coating resistance and used it to character the failure results of organic coatings protection system. Finally, analyzed organic coating protection system failure mechanism by using some modern instrumental analysis methods.The results showed that:the integrated comprehensive model can better evaluate the failure of coating system, and the weight coefficient range that made a higher adaptability to the integrated comprehensive model; coating resistance got by electrochemical methods confirmed the reasonableness of the evaluation system.The SEM observation found that the surface of coating did happen bubble and crack, even section stripping after eight cycles accelerated corrosion experiments. Through EDS analysis, it was found that Cl" of the corrosion coating increased and C/O decreased significantly; what was also found was that the more serious corrosion and this trend was more obvious; In addition, it was found that Cl- decreased with the depth of penetration of corrosive medium in section of corrosion. The filler titanium dioxide also gradually loss due to the destruction of the active components of the coating. FITR analysis showed that the three kinds of organic coatings have the same corrosion mechanism, and the resin strand of N-H bond and C-O bond breaks.Therefore, it could be inferred that the effective components of the coating were destroyed under the photochemical action, which would accelerate the corrosion media such as chloride ion penetrate into the coating and then made the coating occur, such as bubbling, cracking and spalling. The corrosion resistance of the coating system could be greatly improved by the modification of the film coating material and the addition of titanium dioxide in the coating.The uncoated carbon steel system whose surface only treated by supersonic flame spraying was serious corrosion after four cycles accelerated experiment, Through the analysis of XPS, Fe elements were not found in surface coating of carbon steel system before the experimentare but it found after corrosion and which were in the form of the FeO, Fe3O4, Fe2O3, FeOOH, Fe2(SO4)3 five kinds of oxides; the content of two valent iron in parts that corrosion was not serious was more than the parts where corrosion was serious, while the content of Fe2(SO4)3 in the serious corrosion parts was more than the no serious parts, thenthe conversion process of iron may be from a stable Fe element and two iron oxide, through the middle of ferric oxides, and finally were in the form of ferric sulfate; The failure of supersonic flame spraying coating also showed that the content of element C/O would become smaller after corrosion, C may be in the form of oxides left from the coating, the protective of supersonic flame spraying coating gradually lost, the base metal is constantly subjected to the destruction of corrosion medium. |
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