High velocity arc spraying (HVAS) process was used to deposit Al-Ni-Y-Co amorphous and nanocrystalline composite coating on AZ91 magnesium alloy substrate. The microstructure of the coating was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) equipped with energy dispersive spectrometer (EDS) and transmission electron microscopy (TEM). The results show that the coating with thickness of 500 mm presents a dense layered structure with low porosity (1.8%). The coating consists of amorphous, nanocrystalline, and crystalline phases. The microhardness was measured by a microhardness tester. The average values of Vickers hardness for the Al-Ni-Y-Co coating, pure Al coating and AZ91 alloys are about HV 0.1 310, HV 0.1 70, and HV 0.1 60, respectively. The electrochemical corrosion resistance of the coating in 5 wt% NaCl aqueous solution was also investigated, and the results showed that the Al-Ni-Y-Co coating exhibits better corrosion resistance than pure Al coating and AZ91 magnesium alloy.

X. Chen (2009) Microstructure and corrosion behaviour of arc sprayed Zn-Al-Mg-RE cathodic protection coatings on steel substrates, International Heat Treatment and Surface Engineering, 3:1-2, 70-74, Cored wires and high velocity arc spraying technologies have been used to produce Zn-Al-Mg and Zn-Al-Mg-RE (where RE is rare earth) coatings on A3 steel. The durability of coatings in terms of corrosion resistance is the focus of this paper. To study the effect of RE, Zn-Al-Mg coatings also have been produced as a comparison. The microstructures of original coatings and corroded coatings have been investigated after corrosion tests by SEM and XRD. The potentiodynamic polarisation and electrochemical impedance spectroscopy techniques were carried out to determine the corrosion behaviour of the two coatings in 5% NaCl solution. Metallographic as well as electrochemical corrosion results illustrate that the coatings possess a self-sealing capacity, and that the corrosion products can refine the microstructure and enhance the corrosion resistance. Compared to the Zn-Al-Mg coating, the Zn-Al-Mg-RE coating presents a more obvious and stable self-sealing process.