| 摘要: |
| 普通阳极氧化膜难以对铝合金形成有效的防护作用，须进行封孔处理以改善膜层耐蚀性差问题。采用原位生长法制备的层状双金属氢氧化物（LDH）膜对阳极氧化（AAO）膜进行封闭，得到 LDH / AAO 复合膜层，研究阳极氧化电解液中三价铈盐浓度对 AAO 膜层及 LDH / AAO 复合膜层耐蚀性影响。利用扫描电子显微镜（SEM）、能谱仪（EDS）、 辉光放电发射光谱仪(GDOES)分别表征膜层的微观形貌和元素组成，通过电化学交流阻抗（EIS）、动电位极化曲线和酸性盐雾试验检测膜层的耐蚀性。结果表明，在阳极氧化电解液中添加铈盐能够提高 AAO 膜层的致密性和耐蚀性， 并改善后续 LDH 膜层在 AAO 膜表面的生长。LDH 可以在 AAO 孔洞和缺陷中生长，并完全覆盖 AAO 层，耐蚀性明显优于铈盐封闭，铈盐浓度为 0.03 mol / L 时 AAO 膜层与 LDH / AAO 复合膜层耐蚀性更好。通过对 LDH 层负载钒酸根缓蚀剂，进一步优化了复合膜层的耐蚀性能。复合膜层的耐蚀作用主要归因于电解液中添加铈盐提高了 AAO 内层的物理阻隔性能，负载钒酸根的 LDH 外层对腐蚀性离子的捕获及对层间缓蚀剂的释放双重作用为基体铝合金提供了长效保护。提出层状双金属氢氧化物 / 阳极氧化复合膜层，并采用“纳米容器”负载缓蚀剂策略进一步提升复合膜层耐蚀性能。 |
| 关键词: 铝合金 层状双金属氢氧化物 阳极氧化 缓蚀剂 耐蚀性 |
| DOI：10.11933/j.issn.1007?9289.20221104001 |
| 分类号:TG156；TB114 |
| 基金项目:北京市自然科学基金资助项目（2182017，2202017） |
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| Effect of Cerium Salt in Electrolyte on Corrosion-resistance of LDH / AAO Composite Coating |
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ZHANG You1, CHEN Chuping1, ZHANG Zheng1, ZHAO Xuejie1, WEN Chen2, CHEN Fei1
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1.College of New Materials and Chemical Engineering, Beijing Institute of Petrochemical Technology,Beijing 102617 , China;2.Beijing Spacecrafts Manufacturing Factory Co., Ltd., China Academy of Space Technology,Beijing 100094 , China
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| Abstract: |
| It is difficult for a common anodic oxidation(AAO) coating to protect an aluminum alloy; sealing treatment or adding a corrosion-inhibitor to the AAO electrolyte is required to improve the poor corrosion-resistance of the coating. Rare-earth cerium salt is a green and efficient cathodic corrosion-inhibitor for aluminum alloys. It can increase the thickness of the anodic oxide coating, extend corrosion pathways, and improve the pitting-resistance of the coating. A layered double-hydroxide(LDH) is a type of host–guest two-dimensional nano-layered hydroxide material. As a nano-container, it can load a large number of corrosion inhibitors, with intelligent release on the surface of aluminum alloy. In this paper, an AAO coating containing Ce3+ was obtained by adding cerium salt to the electrolyte. On this basis, an LDH coating was prepared using an in situ growth method to seal the AAO, resulting in an LDH / AAO composite coating. The effect of trivalent cerium salt concentration in the anodic oxidation electrolyte on the corrosion-resistance of AAO film and LDH / AAO composite film was studied. The corrosion-resistance of the LDH / AAO composite coating was further improved by loading a vanadate inhibitor on the outer LDH layer for active anti-corrosion of the coating. The microscopic morphology and elemental composition of the films were characterized by scanning electron microscopy (SEM), energy spectrometry(EDS), and glow discharge emission spectrometry(GDOES). The corrosion-resistance of the films was examined by electrochemical alternating current impedance(EIS), kinetic potential polarization curve analysis, and an acid salt spray test. The results show that the corrosion-resistance of the coating was improved by adding cerium salt as a corrosion inhibitor in the anodic oxidation electrolyte. The porous anodic oxide layer was sealed by LDH and improved the growth of the LDH coating on the AAO coating surface. LDH can grow in AAO holes and defects, and completely cover the AAO layer. The corrosion-resistance was significantly better than that of cerium-salt sealing. When the concentration of cerium salt was 0.03 mol / L, the corrosion-resistance of the LDH / AAO composite coating had the highest impedance and better resistance to acid salt spray. It was demonstrated that 0.03 mol / L cerium salt can effectively improve the corrosion-resistance of the coatings. After loading vanadate in the LDH layer, the self-corrosion current density decreased by more than two orders of magnitude and the corrosion rate decreased significantly compared with that of AAO samples. The corrosion-resistance of the composite coating was further optimized by adding vanadate corrosion-inhibitor to the LDH layer. The corrosion-resistance of the composite coating is mainly attributed to addition of cerium salt to the electrolyte to improve the physical barrier properties of the AAO inner layer. Thus, addition of cerium salt to the anodic oxidation electrolyte can improve the density and corrosion-resistance of the AAO coating and improve the growth of the LDH coating on the AAO coating surface. The dual effects of LDH loaded with vanadate to trap corrosive ions in the outer layer and release the interlayer corrosion inhibitor provide long-lasting protection of the substrate aluminum alloy. A layered bimetallic hydroxide anodic oxidation composite coating was proposed and a “nano-container” was successfully used to load the vanadate corrosion-inhibitor. |
| Key words: aluminum alloy layered double hydroxides anodic oxidation corrosion inhibitors corrosion resistance |
