The corrosion of magnesium alloys occurs easily in the South China Sea because of high temperatures, high humidity, high sea salts, and high ultraviolet radiation. Corrosion leads to the failure of materials and structures.
With that in mind, a research team led by Baorong Hou, a professor from the Institute of Oceanology of the Chinese Academy of Sciences (IOCAS) (Qingdao, China), recently researched the corrosion behavior of Mg-Y-Nd-Zn-Zr magnesium alloys in the harsh South China Sea environment. The research was funded in part by Chinese government entities.
In their work, the corrosion resistance of different alloys was analyzed via weight loss rate and electrochemical measurements in the laboratory. According to the team, the Mg-5Y-1.5Nd-xZn-0.5Zr magnesium alloy exhibited the best corrosion resistance, depending on the microstructure, type, and distribution of precipitated phases.
The corrosion resistance of the magnesium alloys in the typical marine environment was as follows: Mg-5Y-1.5Nd-6Zn-0.5Zr < Mg-5Y-1.5Nd-0.5Zr < Mg-5Y-1.5Nd-2Zn-0.5Zr < Mg-5Y-1.5Nd-4Zn-0.5Zr.
The researchers investigated the microstructure of the alloys in order to explain the corrosion mechanisms. The standard electrode potential of rare earth elements was more negative than that of pure magnesium. According to the research team, the precipitated phases in the magnesium alloys containing rare earth elements could influence the micro-anode.
“Some special anodic precipitated phases exhibited biaxial synergistic effect, micro-galvanic corrosion acceleration, and corrosion barrier,” says Jiang Quantong, the study’s first author. “This can improve the corrosion resistance of (the) magnesium matrix, to some extent.”
“Regulating the microstructure, type, and distribution of precipitated phases in magnesium alloys containing rare earth to improve both the mechanical strength and corrosion resistance needs further study,” Hou adds.
The research was supported by National Natural Science Foundation of China for Exploring Key Scientific Instrument, the Open Funds of the State Key Laboratory of Rare Earth Resource Utilization, and Hainan Province Science and Technology Special Fund for providing support.
Source: IOCAS, english.qdio.cas.cn.