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Highlights: [•] The as-received microstructure of bulk Fe2B comprises iron and silicon borides. [•] The orientation of Fe2B in liquid zinc strongly affects on corrosion resistance. [•] The Fe2B/FeB phase transition process of bulk Fe2B in liquid zinc occurs. [•] Phase transition and spalling dominate corrosion of Fe2B in liquid zinc. [Copyright &y& Elsevier]

Abstract: In order to investigate the effects of boron concentration on the corrosion resistance of Fe–B alloys in molten zinc, Fe–B alloys, with the boron concentrations of 1.5wt.%, 3.5wt.% and 6.0wt.% respectively, were dipped into a pure molten zinc bath at 460°C and kept in different time intervals. The results show that, in comparison with 1Cr18Ni9Ti stainless steel, Fe–B alloy with 3.5wt.%B exhibits excellent corrosion resistance, due to the dense continuous network or parallel Fe2B phase which hinders the Fe/Zn interface reaction in Fe–B alloys. The energy dispersive spectrum (EDS) results indicate that the coarse and compact δ phase with the length about 40μm generates near the matrix of Fe–B alloy and massive ζ phase occurs close to the liquid zinc. The corrosion process includes Fe/Zn reaction and the isolation and fracture of Fe2B. The failure of boride is mainly caused by the microcrack. [Copyright &y& Elsevier]

Abstract: The effects of chromium addition on the corrosion resistance of Fe–3.5B alloy in liquid zinc bath at 520°C have been investigated. The results show that the matrix of as-cast Fe–3.5B alloy transforms into α-(Fe, Cr) solid solution while the eutectic Fe2B changes into M2B-type boride gradually with the increasing chromium addition. The corrosion resistance of Fe–3.5B alloy can be greatly enhanced by 5wt.% chromium addition that still maintains the netlike structure of boride in it. EDX analysis reveals that the Cr element can enrich in the Γ-Fe3Zn10Cr x (x =1.09 to 1.37) phase of the interface to hinder the diffusion of zinc atoms favorably. The Cr addition has no effect on the Vickers hardness of δ and ζ in the corrosion layer basically. Corrosion mechanism of Fe–3.5B alloys with various Cr additions includes the following processes: the superficial dissolution of Cr at the interface, dissolution of the Cr-depleted zones of the matrix corroded by liquid zinc, and the spalling of boride which lost the supporting role of the matrix completely. The corrosion process is mainly controlled by the diffusion of liquid zinc atoms. [Copyright &y& Elsevier]