Corrosion Protection of A3 Steel with Zn-Al-Mg-RE Coating from Arc Spraying

Abstract:

Cored wires and high velocity arc spraying (HVAS) technologies have been applied to produce Zn-Al-Mg-RE coating on A3 steels. The durability of coating in terms of corrosion resistance is the focus of this paper. The detailed degradation mechanism has been investigated using electrochemical-monitoring techniques supported by precise pre-test and post-test microscopical examination using Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD). Zn-Al-Mg-RE coating shows a typical aspect of layered heterogeneous structure, the existing of ZnAl2O4 and MgAl2O4 implies the good anti-corrosion feature. The polarization curves showed that Zn-Al-Mg-RE coating exhibits passive behavior at 0.5h and 16h immersion, but at 600h, it begins to dissolute. In contrast, the anti-corrosion performance isn’t cut down. The corrosion potential moves to the noble direction step by step, along with the current density drops gradually. After corrosion, it has been observed that the coating surface is jointed by flaky lamellar products and dense without obvious defects and pores. It is postulated that with the addition of RE, the porosity of the coating is reduced, meanwhile, the stability of the products layer can reinforce the self-sealing effect of the coating distinctively.