离子辅助蒸发沉积镀铝膜的结构及耐腐蚀性

Microstructure and corrosion resistance of aluminum film deposited by ion assisted thermal evaporation

利用离子辅助热蒸发在45钢基材上制备纯铝防护膜,并对其进行喷丸+化学转化后处理。采用中性盐雾机、电化学工作站、扫描电镜、能谱仪对基体及镀铝试样的结构和性能进行研究。结果表明:45钢上铝膜厚度约12μm,膜层晶粒均匀,大小为1~2μm,膜层基体界面紧密,结合良好,膜基之间存在3μm厚的扩散层,扩散层的存在能显著提高基体的耐腐蚀性能。镀铝试样自腐蚀电流比基体低两个数量级,达到1.46×10-6A·cm-2,经盐雾试验1800 h,铝膜部分剥落,没有出现红锈。经过后处理(喷丸+化学转化)镀铝试样,膜层表层致密度提高,并生成一层耐腐蚀转化膜,耐蚀性能得到进一步提高,自腐蚀电流比基体低3个数量级达,达到2.3×10-7A·cm-2,经盐雾试验1800 h后,膜层较完整,没有出现腐蚀严重部位。

Pure aluminum protective film was prepared on the surface of 45 steel substrate by ion assisted thermal evaporation,and it was treated by shot peening and chemical conversion. Microstructure and properties of both the aluminum film and the substrate were studied by neutral salt spray machine,electrochemical workstation,scanning electron microscope,energy disperse spectroscopy. The results show that the thickness of aluminum film is 12 μm,and the grain size is uniform which is 1-2 μm. The film is closely well bonded with the matrix materials. There is a 3 μm thickness diffusion layer between the film and the substrate which can significantly improve the corrosion resistance of the substrate. The corrosion current of aluminum protected sample is 1. 46 × 10^-6 A·cm^-2,which is 2 orders of magnitude lower than that of substrate. After 1800 h salt spray test,the aluminum film spalled partially,but without rust. After shot peening and chemical conversion treatment,the density of the film is improved and a corrosion resistant conversion film is formed,and the corrosion resistance is further improved. The corrosion current is 2. 3 × 10^-7 A·cm^-2,which is 3 orders of magnitude lower than that of substrate,and the film is more complete,no severe corrosion occurred after 1800 h salt spray.