| CUI Jing,LU Meng-ke,LI Hu-lin,ZHANG Hang,ZHAI Wei,PANG Ming,YANG Guang-feng.Corrosion Behavior and Mechanism of Vermicular Graphite Cast Iron in Neutral Salt Spray[J],49(6):267-275 |
| Corrosion Behavior and Mechanism of Vermicular Graphite Cast Iron in Neutral Salt Spray |
| Received:September 09, 2019 Revised:June 20, 2020 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2020.06.032 |
| KeyWord:vermicular graphite cast iron neutral salt spray corrosion electrochemical corrosion mechanism corrosion appearance evolution of rust layers |
| Author | Institution |
| CUI Jing |
Civil Aviation University of China, Tianjin , China |
| LU Meng-ke |
Civil Aviation University of China, Tianjin , China |
| LI Hu-lin |
Civil Aviation University of China, Tianjin , China |
| ZHANG Hang |
Civil Aviation University of China, Tianjin , China |
| ZHAI Wei |
Civil Aviation University of China, Tianjin , China |
| PANG Ming |
Civil Aviation University of China, Tianjin , China |
| YANG Guang-feng |
Civil Aviation University of China, Tianjin , China |
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| Abstract: |
| The work aims to reveal the atmospheric corrosion behavior of vermicular graphite cast iron (VGCI) and clarify the corrosion law and corrosion mechanism. Accelerated salt spray corrosion experiments were carried out in laboratory, and the results were characterized by weight loss, SEM/EDS, XRD and electrochemical methods. The cross section of VGCI had obvious stratification in neutral salt spray. The corrosion rate was 0.53 mg/(cm2×h) in the early stage, and then fluctuated in the later stage, but the overall stability tended to be 0.36 mg/(cm2×h). The corrosion potential (Ecorr) of the vermicular graphite cast iron rust sample decreased first and then increased from -680 mV to -600 mV, and the change trend of the polarization resistance (Rp) was consistent with the corrosion potential (Ecorr). The self-corrosion current (Icorr) had obvious fluctuations throughout the corrosion cycle and the corrosion products of VGCI in neutral salt spray were: Fe(OH)3, Fe2O3, FeOOH and a small amount of Fe3O4 as well as metal carbide Fe2C. VGCI can be developed into comprehensive corrosion after 84 h in neutral salt spray environment, with gully appearance and the microscopic appearance of corrosion products is shown in clusters and lamella. In the early stage of corrosion, an oxide film is formed on the surface of the matrix due to electrochemical corrosion, and the corrosive medium corrodes the matrix along the graphite to generate internal stress, resulting in the fracture of the outer rust layer. At the same time, the corrosion products on the worm-like graphite are in loose clusters. The two together forms the medium mass transfer channel, making the corrosion easier to develop. |
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