Liu Junyi, Huang Xiaohu, Ren Yi, Wong Lai Mun, Liu Hongfei, Wang Shijie
Institute of Materials Research and Engineering (IMRE), A*STAR (Agency for Science, Technology and Research), 2 Fusionopolis Way, Singapore, 138634, Singapore.
Sci Rep. 2022 Mar 16;12(1):4532. doi: 10.1038/s41598-022-08727-7.
Al-alloy/carbon fibre reinforced polymer (CFRP) joint systems offer exceptionally lightweight, superior fatigue behaviour and impact resistance for aerospace applications. Nevertheless, the galvanic corrosion at the joint interfaces accelerates the adhesive failure and strength damage. In this work, oxidation of Al 7075 alloy was studied by employing plasma electrolytic oxidation (PEO) and thin film sulphuric acid anodizing (TFSAA) methods, addressing their galvanic corrosion (GC) protection performance in contact with CFRP. Structural and electrochemical characterisations were carried out in tandem with varied oxidation process parameters, revealing that high voltage PEO resulted in crystallized compact ceramic coating and thus improved GC protection. A decrease in the GC current by ~ 90% has been achieved by using the PEO coating at 700 V compared with the ~ 12% current reduction of commercial TFSAA coating. Further microstructure studies revealed that the improved GC protection of the crystallized PEO coating was realized by suppressing the initiation and propagation of localized pitting due to the improved electrical isolation between the Al-alloy/CFRP interfaces. A high voltage PEO process provides sufficient energy to produce uniform and crystalline ceramic coating consisting of AlO and mullite, which give rise to improved corrosion protection.
铝合金/碳纤维增强聚合物（CFRP）连接系统为航空航天应用提供了极其轻质、卓越的疲劳性能和抗冲击性。然而，连接界面处的电偶腐蚀会加速胶粘剂失效和强度损伤。在这项工作中，采用等离子体电解氧化（PEO）和薄膜硫酸阳极氧化（TFSAA）方法研究了7075铝合金的氧化过程，探讨了它们与CFRP接触时的电偶腐蚀（GC）防护性能。结合不同的氧化工艺参数进行了结构和电化学表征，结果表明高电压PEO可形成结晶致密的陶瓷涂层，从而提高了GC防护性能。与商业TFSAA涂层使GC电流降低约12%相比，使用700V的PEO涂层可使GC电流降低约90%。进一步的微观结构研究表明，由于铝合金/CFRP界面之间的电绝缘性提高，抑制了局部点蚀的萌生和扩展，从而实现了结晶PEO涂层GC防护性能的改善。高电压PEO工艺提供了足够的能量，以产生由AlO和莫来石组成的均匀结晶陶瓷涂层，从而提高了耐腐蚀性能。
