新型Al2O3/BTESPT/rGO复合涂层制备及长效耐腐蚀性能研究

DOI:PreparationandLong-TermCorrosionResistanceofNovelAl2O3/BTESPT/rGOCompositeCoatings

摘要:

针对7075Al铝合金在海水中耐腐蚀性较差的问题，首先采用阴极液相等离子电解技术制备氧化铝（Al₂O₃）涂层，实现对铝合金基体的整体包覆；针对Al₂O₃涂层存在的微裂纹和微孔洞等缺陷，通过浸渍提拉和脉冲电沉积技术继续沉积双-［3-（三乙氧基）硅丙基］四硫化物（BTESPT）硅烷涂层和还原氧化石墨烯（rGO）涂层，进一步提高7075Al铝合金的长效耐腐蚀性能。对沉积涂层的物相组成、表面形貌、电化学性能以及在海水中浸泡后的阻抗值和宏观表面形貌进行了分析。结果表明，单层Al₂O₃涂层包覆的铝合金在海水中浸泡25 d后阻抗值仍高达4.6 Ω·cm²，远远高于7075Al铝合金的3.2 Ω·cm²，但Al₂O₃涂层中的微裂纹和微孔洞等缺陷为海水中氧离子和氯离子提供了扩散通道，使铝合金表面形成了腐蚀斑点；采用脉冲电沉积技术在0.8 V制备的Al₂O₃/BTESPT/rGO复合涂层均匀、致密的覆盖在7075Al铝合金表面，并填充了Al₂O₃涂层表面的微观孔洞和裂纹，复合涂层包覆的7075Al铝合金具有最正的腐蚀电位和最小的腐蚀电流密度，表明其腐蚀倾向和腐蚀速率最小；在海水中浸泡105 d过程中，其阻抗值在5.44~5.71 Ω·cm²间波动，复合涂层表面仅出现了轻微的颜色变化，没有观察到明显的腐蚀痕迹，表现出优异的长效海水耐腐蚀性能。

Abstract:

To improve the long-term corrosion resistance of 7075Al aluminum alloy, an alumina (Al₂O₃) coating was prepared first by cathodic liquid plasma electrolysis technology to achieve full coverage of the aluminum alloy substrate, and then a bis[3-(triethoxysilyl)propyl]tetrasulfide (BTESPT) silane coating and reduced graphene oxide (rGO) coating (BTESPT/rGO composite coating) was further prepared on the surface of the Al₂O₃ coating via dip coating and pulsed electrodeposition technology to fill the micro-cracks and micro-holes in the Al₂O₃ coating, further improving the long-term corrosion resistance of 7075Al alloy. The phase composition, surface morphology, electrochemical properties, impedance value and macroscopic surface morphology of the deposited coatings were analyzed. The results indicate that the impedance value of 7075Al coated with a single Al₂O₃ coating is still 4.6 Ω·cm² after immersion in seawater for 25 d, which is significantly higher than 3.2 Ω·cm2 of 7075Al alloy. However, several etch pits are formed on the Al₂O₃ coating because the oxygen and chloride ions in seawater enter the interior of 7075Al alloy through the micro-cracks and micro-pores in the Al₂O₃ coating. In contrast, the uniform and dense Al₂O₃/BTESPT/rGO composite coating, prepared by the pulsed electrodeposition technique at 0.8 V deposition voltage, fills the micro-cracks and micro-pores generated in the process of Al₂O₃ coating deposition. The 7075Al alloy coated with the composite coating exhibit the most positive corrosion potential and the lowest corrosion current density, indicating the lowest corrosion tendency and corrosion rate. Throughout the period of immersion in seawater for 105 d, the impedance value of 7075Al coated with Al₂O₃/BTESPT/rGO composite coating varies within the range between 5.44 Ω·cm² and 5.71 Ω·cm². Furthermore, the Al₂O₃/BTESPT/rGO composite coating exhibits only slight color change on its surface, demonstrating excellent long-term corrosion resistance in seawater.