Effects of Minor Ge on the Microstructure and Corrosion Resistance of Zn-2Al Filler Metals

The properties of flux-cored Zn-Al filler metals are prone to deteriorating due to corrosion, making filler metals unusable. In this study, flux-cored Zn-2Al-<i>x</i>Ge (<i>x</i> = 0, 0.3, 0.5, and 0.8 wt.%) filler metals are prepared to explore the effect of minor Ge on the corrosion resistance of Zn-2Al filler metals. The salt spray test is carried out on filler metals. A scanning transmission electron microscope is used to identify the phases in filler metals. The electrochemical performance of filler metals was tested by a workstation. The findings indicate that the microstructure of the Zn-2Al filler metal is composed of α-Al and η-Zn. Diamond-Ge forms in the microstructure of the Zn-2Al filler metal due to the introduction of Ge. Zn-2Al-<i>x</i>Ge filler metals exhibit pitting corrosion characterized by intergranular corrosion (IGC) in the salt spray environment. Ge improves the IGC resistance of filler metals by changing the distribution of α-Al in the filler metal. The Zn-2Al-0.3Ge filler metal demonstrates the most excellent corrosion resistance. It has 16% elongation after 15 d of corrosion, which is higher than that of Zn-2Al by 13.6%.