Research And Application Of Corrosion Resistance Mechanism To Molten Zinc Of Iron-Base Alloy

The metallic corrosion of molten zinc is always the most difficult problem to be solved, so ceramic zinc pot is in general use in order to reduce the corrosion of molten zinc to pot in hot-dip galvanizing industrial. But because of the poor thermal conductance, ceramic pot is unable to adapt to exterior heating. Therefore, ceramic zinc pot adopts to interior heating mostly.But now there are no ideal materials with both excellent corrosion resistance to molten zinc and mechanical behavior under high temperature to be used in outer shell of internal heater, thus, the application and generalization of interior heating technology are limited greatly. This paper researched the preparation of alloys with corrosion resistance to molten zinc based on the ferroalloy.Fe-Al-B alloys were studied in the paper, result shows that the B and Al elements have a great influence on corrosion resistance and mechanical behavior under high temperature of the materials. Through the optimization of alloying composition, the contents of B and Al in alloys are determined. Fe-Al-B alloys have a good corrosion resistance to molten zinc, the Fe-B eutectic structure hinders zinc atoms diffusing to alloy matrix, which reduces the corrosion rate of alloys.The corrosion interface of alloys in molten zinc is observed and analysed by SEM, XRD and TEM, result shows that the corrosion of alloys in molten zinc is intercrystalline corrosion, the diffusion of zinc atoms are mainly along the grain boundary. The molten zinc reacts with a-phase of Fe-Al-B alloys, and forms Fe-Zn intermetallic compound, which can easily dissolve in molten zinc under high temperature. So the Fe-B eutectic structure will breakdown and drift to molten zinc under the scouring of molten zinc.The paper analysed the thermodynamic and dynamic process of Fe-Zn reaction, result shows that the corrosion of iron base alloys in molten zinc is a spontaneous process, and the corrosion rate is influenced by multiple factor. Reducing the free energy is the key to increase the corrosion resistance of the alloys.After adding C, Ti or V, the microstructure of Fe-Al-B alloys is refined, and TiC or VC particles that disperse in matrix increase the bend strength and mechanical behavior under high temperature. Continue adding Mo, W element to alloys, there forms (MoW)₂FeB₂ phase that hasexcellent corrosion resistance to molten zinc, it disperses in grain boundary and hinders zinc atoms from diffusing to alloy matrix. So the corrosion rate of alloys slows down.Carry on the industrialized test in the hot-dip galvanizing workshop to interior heater that made of iron base complex alloys, test result shows that the heater can have worked for half years steadily in the liquid zinc. The material that has excellent corrosion resistance to molten zinc and fine mechanical behavior can meet the needs of hot-dip galvanizing industrial.