Research on Microstructure and Corrosion Behavior of Zinc-Magnesium Coating by Powder Impregnation

Abstract

Abstract In order to improve the service life of railway fasteners under various environmental conditions, the Zn and Zn-Mg coating were prepared on the railway fastener gaskets by powder impregnation. XRD and SEM were used to characterize the phase composition, microstructure and morphology before and after the salt spray. The neutral salt spray test (NSST) and the electrochemical workstation were used to characterize the corrosion resistance of the two coatings. Results show that there was a large area of red rust on Zn coating after 480 hours of NSST, while there was no red rust on Zn-Mg coating after 1920 hours of NSST. The impedance of the Zn-Mg coating reached 1015.6 Ω·cm2, about 3.65 times of the Zn coating. Zn-Mg coating’ current density was 3.27 μA·cm−2, which was only 21% of the Zn coating. MgZn2 and Mg2Zn11 phases were easier to formed in Zn-Mg coating due to the infiltration of magnesium, forming a dense and protective layer, thereby greatly improved its corrosion resistance.