6061铝合金表面ZnAl-LDHs层的制备及其耐腐蚀性能

Preparation and Corrosion Resistance of the ZnAl-LDHs Film on 6061 Al Alloy Surface

采用原位生长的方法,首先在6061铝合金表面制备了层间含NO3-的ZnAl-LDHs (layered double hydroxides,层状双金属氢氧化物)层,然后将正钒酸根(VO43-)和偏钒酸根(VO3-) 2种缓蚀剂离子插入ZnAl-LDHs-NO3层板间,在6061铝合金表面制备了ZnAl-LDHs-VO4和ZnAl-LDHs-VO3层。通过XRD、FT-IR和SEM等技术研究了上述3种ZnAl-LDHs层的晶体结构、成分组成和表面形貌,并分析了ZnAl-LDHs层的生长行为;通过电化学工作站和超景深3D视频显微镜研究了6061铝合金表面3种ZnAl-LDHs层在3.5%NaCl水溶液中的耐腐蚀行为。结果表明,6061铝合金表面原位制备的ZnAl-LDHs层呈片状垂直于基体生长,能够完全覆盖在铝合金表面。与6061铝合金基体相比,含ZnAl-LDHs层的铝合金具有较高的腐蚀电位(Ecorr)、较小的腐蚀电流(Icorr)和较大的电荷转移电阻(Rct)。这说明ZnAl-LDHs层能够明显提高6061铝合金的耐腐蚀性能,可用于6061铝合金表面的防腐蚀保护。在6061铝合金表面的3种ZnAl-LDHs层中,ZnAl-LDHs-VO3的耐腐蚀性能最高。

6061 Al alloy is widely used for structural components in the structural, building, aerospace and automobile industry because of their good extrude-ability, high strength and low density. 6061 Al alloy is easily corroded during the corrosive environments containing Cl-, which lead to the decreasing of the alloy service life. Therefore, the Al alloy need to adopt surface treatment to improve the corrosion resistance. The chromate passivation was the most effective surface treatment technology of Al alloys in the past. However, Cr（VI） could pollute the environment and harmful to human body. Thus, it is necessary to develop chromium-free films to protect Al alloy. Layered double hydroxides （LDHs） are an environment-friendly and smart material, which could be used for anticorrosion film. The inhibitor can be inserted into the film layer due to its unique anion exchanging capacity. Therefore, the LDHs is acquired self-healing performance and applied to the anticorrosion field of Al alloy. Meanwhile, vanadate is a good inhibitor and it has many forms under different pH conditions. Moreover, different forms of vanadate have different influence on LDHs film. The corrosion resistance of LDHs and its modified form films on Al alloys need deep study. In this work, ZnAl-LDHs films with NO3- were prepared on the suface of 6061 Al alloy via a facile in-situ growth method, and then ZnAl-LDHs-NO3 films were intercalated with the corrosion inhibitor VO43- and VO3- to obtain the ZnAl-LDHs-VO4 and ZnAl-LDHs-VO3 films, respectively. The structure, morphology and composition of as-prepared ZnAl-LDHs films were investigated by XRD, fourier infrared spectrometer （FT-IR） and SEM; the corrosion behavior of ZnAl-LDHs films in the 3.5%NaCl （mass fraction） solution were studied by the electrochemical workstation and the 3D microscope. The results show that the plate-like ZnAl-LDHs microcrystals are perpendicular to the substrate and cover almost the entire Al alloy substrate surface. Compared with the 6061 Al substrate, ZnAl-LDHs films can not only decrease the corrosion current （Icorr）, but also increase the corrosion potential （Ecorr） and charge transfer resistance （Rct） of the 6061 Al alloy. It is suggested that ZnAl-LDHs films could significantly enhance the corrosion resistance of 6061 Al substrate, indicating an effective protection for 6061 Al alloy by the ZnAl-LDHs film. The ZnAl-LDH-VO3 film is of the highest corrosion resistance in the studied ZnAl-LDHs films.