The Phase Relations Of The Zn–Co–Sb Ternary System

Steel is a widely used metallic materials, but it is easy to rust and corrosion. Hot galvanizing is an efficient and economical method used for anti-corrosion of steels. It is now widely used owing to its simple and ripe technology, and excellent anticorrosion behavior. With the development of society, people’s quality of life requirements increase, the requirements of hot-dip galvanized products is also increasing. So, we not only ensure the coating quality, but also to improve their appearance and plasticity.Adding alloying elements into zinc bath as an effective way to changing the structure and properties of coating. Researchers have been a lot of research in this area such as Al、Ni、Pb、Bi、Co、Sb. Some studies have found that adding the right amount of Co can inhibit the thick coating and obtain dense coating, then to increase corrosion resistance. However, the original intention of add Sb element was to replace Pb. Long time ago, Pb is an effective additive element, but it was forbidden to used because of its toxic. Later it was found that Sb has a similar function with Pb and even better than Pb. Sb elements can makes the molten zinc more fluid and reduces the loss of zinc,meanwhile promotes the formation of spangle in the coating surface to improve product appearance. To some extent, it can improve the intergranular corrosion resistance of the coating. Consequently, it needs to determine the 450℃and 600℃isothermal section of Zn-Co-Sb ternary system and study the effect of Co and Sb on hot galvanizing, to provide a basis for the study of Fe-Zn-Co-Sb quaternary system and to develop a new lead-free alloy of galvanizing.The 450°C and 600°C isothermal sections of Zn-Co-Sb ternary system have been determined by equilibrated alloys approach coupled with a scanning electron microscopy and energy dispersive spectroscopy(SEM-EDS) and X-ray diffraction(XRD) and other relevant equipment. The results indicate that a new ternary compound named M(Co Sb Zn) has been found. The M(Co Sb Zn) exists at 450℃ and600 ℃ isothermal section, but the composition range of it have a little changed.Twelve three-phase regions exist in this isothermal section at 450°C, i.e., Co Sb3 +Sb Zn + α-Sb, Co Sb3 + Sb Zn + Sb3Zn4, Co Sb3 + Sb3Zn4 + M(Co Sb Zn), Co Sb2+ Co Sb3+ M(Co Sb Zn), Co Sb2 + Co Sb + M(Co Sb Zn), Co Sb + M(Co Sb Zn) + β1-Co Zn, M(Co Sb Zn) + β1-Co Zn + γ-Co5Zn21, M(Co Sb Zn) + γ-Co5Zn21 + Sb3Zn4, γ-Co5Zn21 +Sb3Zn4 + γ1-Co Zn7.8, Sb3Zn4 + γ1-Co Zn7.8 + γ2-Co Zn13, γ2-Co Zn13 + η-Zn + Sb2Zn3,ε-Co + Co Sb + β1-Co Zn; Nine three-phase regions exist in this isothermal section at600°C, i.e., Co Sb3 + α-Sb + L, L + Co Sb2 + Co Sb3, L + Co Sb2 + M(Co Sb Zn), Co Sb2+ M(Co Sb Zn) + Co Sb, β1-Co Zn + M(Co Sb Zn) + Co Sb, β1-Co Zn + M(Co Sb Zn) +γ-Co5Zn21, L + M(Co Sb Zn) + γ-Co5Zn21, L + γ1-Co Zn7.8 + γ-Co5Zn21, α-Co +β1-Co Zn + Co Sb;...