| 引用本文: | 赵平平,宋影伟,杨丽景,宋振纶.氟离子对ZTi60钛合金损伤钝化膜生长过程的影响[J].中国表面工程,2024,37(6):226~235 |
| ZHAO Pingping,SONG Yingwei,YANG Lijing,SONG Zhenlun.Effect of Fluorine Ions on Film Growth of ZTi60 Titanium Alloy Scratched Surface[J].China Surface Engineering,2024,37(6):226~235 |
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| 摘要: |
| 钛合金由于具有优异的耐蚀性，被广泛应用于海洋工程领域。然而，材料在海洋环境下服役条件恶劣，容易遭受严重的腐蚀破坏。钛合金使用时面临的腐蚀破坏都与钝化膜密切相关，尤其是表面划伤后钝化膜受损引起的局部腐蚀。目前，破损区钝化膜在氟离子 F? 介质中的演化规律尚不清楚。因此，利用电极划伤装置，对比 ZTi60 钛合金在中性含 F? 的 3.5% NaCl 溶液中，完整膜层与划伤区域钝化膜生长的动力学过程。结果表明：完整膜层与划伤钝化膜的载流子密度 ND 皆随 F? 浓度的增加而增加，这表明钝化膜的生长速率随着 F? 浓度的增加逐渐增大。对于完整钝化膜，膜层的生长是由氧空位 V?的生成反应决定的。相同 F? 浓度下，电场强度随着膜厚的增加而逐渐增大，供体迁移变得困难，膜生长速度减慢。对于划伤钝化膜， 受损钝化膜的划伤区域储存更多的变形能，膜层中的缺陷密度远远高于其他区域，划伤区域氧空位 V? 的消耗速率成为膜层生长的速率控制步骤。在钝化膜再钝化过程中，F? 与溶解氧对钝化膜中氧空位 V? 的消耗反应存在竞争机制，其过程受溶液中 F? 的含量控制。通过探讨 F? 与溶解氧的交互作用对损伤钝化膜再钝化过程的影响规律，为钛合金表面在复杂环境中的安全使用提供了理论依据。 |
| 关键词: 钛合金 表面划伤 Mott-Schottky 曲线 氟离子浓度 载流子密度 |
| DOI：10.11933/j.issn.1007-9289.20231230001 |
| 分类号:TG172 |
| 基金项目:国家重点研发计划（2022YFB3808800） |
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| Effect of Fluorine Ions on Film Growth of ZTi60 Titanium Alloy Scratched Surface |
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ZHAO Pingping1，SONG Yingwei2，YANG Lijing1，SONG Zhenlun1
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1.Key Laboratory of Advanced Marine Materials, Ningbo Institute of Materials Technology and Engineering,Chinese Academy of Sciences, Ningbo 315201 , China ；2.Key Laboratory of Nuclear Materials and Safety Assessment, Institute of Metal Research,Chinese Academy of Sciences, Shenyang 110016 , China
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| Abstract: |
| Titanium alloys are widely used in marine engineering due to their excellent corrosion resistance. However, the service conditions in marine environments are extremely harsh, and the used materials are vulnerable to severe corrosion. Corrosion damage to titanium alloys is closely related to passive films, such as the local corrosion caused by the scratching of the passive film on the surface. Currently, the effect mechanism of scratched passive film on the corrosion process of titanium alloys remains unclear. Therefore, by combining the scratching electrode test and an electrochemical analysis, the corrosion behavior of the ZTi60 titanium passive film after scratching was studied in 3.5wt.% NaCl with different fluorine ion concentrations. The results indicate that,regarding the intact surface of ZTi60, there is an obvious dependent relationship between the Rb and F? concentrations. The Rb values first decrease sharply with an increase in the F? concentration. Then, there is a turning point for the slope when the F? concentration is more than 50 mmol / L. The rate of decrease of Rb becomes slight, compared with that below 50 mmol / L. This value is related to the critical F- concentration. When the F? concentration is lower than the critical concentration, the passive films could resist F? , whereas when the F? concentration is higher than the critical concentration, the oxygen vacancies in the passive film could be occupied by Fand the fluorine-titanium complex are formed by the binding between F? and Ti4+ in the film lattice. According to the M-S results, the ND values increase with an increasing F? concentration, which responds to the growth rate of the passive film at different F? concentrations. Based on the point defect model, the growth of the intact film is determined by the generation of oxide vacancies V?, and the rate of film growth becomes faster at higher F? concentrations, which results in an increasing trend of ND with an increasing F? concentration. Under the same F? concentration, the electric field strength gradually increases with an increasing film thickness. Therefore, the migration of the donor becomes difficult, and the rate of film growth slows. Finally, the ND values decrease over time. Regarding the scratched film, a rapid negative shift of the OCP occurs after scratching, indicating damage to the passive film and the exposure of the active metal. Then, the OCP returns to an uptrend after approximately 1 h, which could be attributed to the regeneration of the damaged passive film. The long return time is related to the low oxygen content of the electrolyte. Moreover, the OCP curves after 1 h exhibits two trends with different F? concentrations. When the F? concentration is lower than 5 mmol / L, the OCP first increases with time and then keeps a relatively stable value at a positive potential. However, when the F? concentration is higher than 5 mmol / L, the OCP declines with time and then keeps a relatively stable values at a more negative potential. The value at which the OCP continued to increase with time defines as the critical concentration, and the critical value of the scratched surface under deficient oxygen is lower than that of the intact surface. The optical and LSCM surface corrosion images of the scratched surface after 24 h of immersion in 3.5% NaCl containing different F? concentrations show that there is no change on the surface when the F? concentration is lower than 5 mmol / L, whereas the areas of the discoloration region gradually increase with an increasing F? concentration when the F? concentration exceeds 5 mmol / L. Furthermore, the discoloration region first develops along the side of the scratch ridges and then spread to both the outside of the scratch and the scratch groove. Discoloration can be associated with damage to the passive films, thereby indicating that the passive film around the scratched regions suffers attack when the F? concentrations exceeds 5 mmol / L. Under these circumstances, the scratch area stores more deformation energy than the surface away from the scratch, thereby resulting in more dislocations.Thus, the consumption rate of oxide vacancies in the scratch region is the determining step of film growth. There is a competitive mechanism between F? and dissolved oxygen in the repassivation process of the passive film. The oxygen vacancies of the passive film are competitively consumed by F? and dissolved oxygen, and the effect is controlled by the concentrations of F- and dissolved oxygen in the electrolyte. When the F? concentration is lower than the critical concentration, the reaction of dissolved oxygen consuming oxygen vacancies is dominant, and the film becomes dense with increasing immersion time. In contrast, when the F? concentration exceeds the critical concentration, the consumption of oxygen vacancies by F? is dominant, which results in corrosion damage to the passive film. Under the same F? concentration, owing to the concentration of oxygen vacancies, the ND values increase with time, in inverse proportion to the partial pressure of oxygen in the electrolyte. |
| Key words: titanium alloy surface scratch Mott-Schottky plots fluorine ions concentrations donor density |
