| WU Hu-lin,ZHANG Zhi-feng,PENG Dong,YANG Zhao,SONG Kai-qiang,CONG Da-long,LI Yi,XIE Yang,CHEN Shuang,HUANG An-wei,LI Zhong-sheng.Microstructure and Galvanic Corrosion Properties of Al2O3-13%TiO2 Insulation and Protection Composite Coatings[J],52(3):266-275, 286 |
| Microstructure and Galvanic Corrosion Properties of Al2O3-13%TiO2 Insulation and Protection Composite Coatings |
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| DOI：10.16490/j.cnki.issn.1001-3660.2023.03.024 |
| KeyWord:atmospheric plasma spraying Al2O3-13%TiO2 coating defects sealing treatment resistance galvanic corrosion |
| Author | Institution |
| WU Hu-lin |
Southwest Institute of Technology and Engineering, Chongqing , China |
| ZHANG Zhi-feng |
Nuclear Power Institute of China, Chengdu , China |
| PENG Dong |
Southwest Institute of Technology and Engineering, Chongqing , China |
| YANG Zhao |
Nuclear Power Institute of China, Chengdu , China |
| SONG Kai-qiang |
Southwest Institute of Technology and Engineering, Chongqing , China |
| CONG Da-long |
Southwest Institute of Technology and Engineering, Chongqing , China |
| LI Yi |
Nuclear Power Institute of China, Chengdu , China |
| XIE Yang |
Nuclear Power Institute of China, Chengdu , China |
| CHEN Shuang |
Nuclear Power Institute of China, Chengdu , China |
| HUANG An-wei |
Southwest Institute of Technology and Engineering, Chongqing , China |
| LI Zhong-sheng |
Southwest Institute of Technology and Engineering, Chongqing , China |
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| Abstract: |
| The work aims to study the galvanic corrosion protection effects of plasma sprayed Al2O3-13%TiO2 coatings and sealed Al2O3-13%TiO2 composite coatings on TC4-H70 dissimilar metal galvanic couples. The phase composition, microstructure and element distribution of the coating were characterized and analyzed by X-ray diffractometer, scanning electron microscope and energy dispersive spectrometer. The corrosion resistance of the coating and the comparative samples were analyzed and studied by electrochemical workstation and galvanic corrosion testing instrument. XRD results showed that the plasma sprayed Al2O3-13%TiO2 coating was composed of α-Al2O3 and γ-Al2O3 phases, with γ-Al2O3 as the main phase. SEM and dynamic potential polarization polarization curve indicated that there were defects such as micro-pores and micro-cracks in the Al2O3-13%TiO2 coating, the corrosive medium was easy to penetrate, and the corrosion current density was (7.0±0.20)×10–5 A.cm–2, which was greater than the corrosion current density of H70 substrate [(4.6±0.63)×10–5 A.cm–2], so the corrosion resistance of Al2O3-13%TiO2 coatings was inferior and cannot provide corrosion protection to the H70 substrate. After sealing treatment, the defects in the surface layer of the Al2O3-13%TiO2 coating were fully filled, and a dense barrier layer with a thickness of about 20-40 μm was formed on the ceramic surface, which effectively blocked the infiltration of NaCl corrosion medium, and the corrosion current density of the coating was only 1.0×10–9 A.cm–2, which was 4 orders of magnitude smaller than that of the H70 substrate and Al2O3-13%TiO2 coating sample, so the corrosion resistance of the coating was dramatically improved. The electrochemical impedance results demonstrated that the arc radius of capacitive resistance was in the order of sealing Al2O3-13%TiO2 coating>H70 substrate>Al2O3-13%TiO2 coating. It can be seen that the sealed Al2O3-13%TiO2 coating possessed the highest charge transfer resistance and the best corrosion resistance. The equivalent circuit analysis results manifested that the interfacial charge transfer resistance between the substrate and the coating of the sealed Al2O3-13%TiO2 coating was 1.9×108Ω.cm2, which was comparable to that of the H70 (5.1×103 Ω.cm2) substrate and the Al2O3-13%TiO2 coating (2.2×103 Ω.cm2) increased by 5 orders of magnitude, indicating that the sealed Al2O3-13%TiO2 coating not only had the best corrosion resistance, but also presented the largest resistance to electron transport. This was beneficial to reduce galvanic corrosion between dissimilar metals. After 15 d galvanic corrosion test of TC4-H70 galvanic couple, the surface of H70 was corroded, and the Al2O3-13%TiO2 coating after sealing treatment could effectively reduce the galvanic corrosion between TC4-H70 galvanic couple. After 15 d galvanic corrosion test, none of the samples corroded and the coating was intact. The excellent galvanic corrosion protection effect of the sealed Al2O3-13%TiO2 coating is mainly due to its high resistance and high surface layer density, which almost block the electron transmission between dissimilar metals to make the effect of galvanic battery between dissimilar metals extremely weak. It can be seen that the coating could effectively prolong the service life of dissimilar metal seawater pipelines, and displace a great application prospect in galvanic corrosion protection. |
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