| Corrosion phenomenon can be found everywhere, it causes serious damage to the daily life and industrial manufacture, which are both a huge horrendous of metals and the countless loss of shutting down and production halts or even threaten to the life and property of people. So corrosion and protection have draw great attention and the metal protection technology has been developed and widely applied.Hot dip galvanizing process has been widely applied in the field of atmospheric corrosion prevention for steel material because that this process is simple and the working life of the clad layer is long. However, new problems appeared with the development of billet continuous casting technology. The productions of the billet continuous casting technology are mostly killed steel or half killed steel with high content of Si. These kinds of steel will lead to the Sandelin effect of murky grey, super-thick and poor adhesion and will result in a quality reduction and cost growth. At present, preparation of clad layer and hot galvanized process are the main techniques to solve the problem.The oil contamination and rust on the surface of the substrate must be cleaned before the zinc plating processes. Traditional preprocess is very complicated. One of the purpose of this topic is to develop a kind of integrated lighting solution which contain the efficacy including working at low temperature and efficiently. This integrated lighting solution can achieve the target of oil removal, rust removal, phosphating and passivation simultaneously. The constituent of the integrated lighting solution were H3PO4320ml·L-1, ZnO10g·L-1, KClO34g·L-1, Zn(H2PO4)210g·L-1, C4H6O6(Dihydroxysuccinic acid)10g·L-1, Zn(NO3)24g·L-1and OP-10(Emulgator)10ml·L-1, which was determined by single factor experiment and orthogonal experiment. All the performances of the integrated lighting solution and the phosphating film on the steel substrate comply with the relevant standards. This lighting solution has many merits including efficient and environment friendly, low cost, simple to use and no toxic ions such as F-, NO2-and Cr6+are included. Besides the steel can be wiped by or immersed in the lighting solution at room temperature. The phosphating film is compact and homogeneously thin, and can prevent the substrate from being rusted and corrosion. The clad layer can be deposited on the substrate directly after preprocess.To solve the problem of Sandelin effect when deposit Zinc layer on the substrate of reactive steel, Sn and Bi which can restrain this effect and increase the flowability was added into the Zinc bath. Zn-Sn-Bi alloy clad layer was deposited using the hot galvanized process. The result of thickness measurement and microstructure observation of the clad layer indicated that the sharp reaction of Fe and Zn was restrained and Sandelin effect was avoid. Clad layer with Sn of5%was significantly thinner than that of Zinc layer. The value of the thickness of the layer decreased further with the Bi content and reached the lowest point when the Bi content of Zinc bath isl%. The clad layer was consist of two layers of8k (compact) and8P (loose). Clad layer of Zn-5%Sn-0.I%Bi possesses a more thick δκ layer and a more compact8P. The grains on the surface of the layer was unique and in alignment. Corrosion experiments including static immersion corrosion experiment in Na2SO4of5%in weight, salt mist test in NaCl of5%in weight and electrochemical corrosion experiment in NaCl of3.5%in weight were carried out. It showed that the corrosion resistance of clad layer of Zn-5%Sn-0.1%Bi was the best and then the Zn layer, clad layer of Zn-5%Sn performed the worst, the result of which was verified by the Contact Angle measurement of the layer under different solution. However, clad layer of Zn-Sn-Bi can restrain the Sandelin effect significantly. But Sn and Bi had no obvious effect on the corrosion resistance of the layer especially in the strong corrosion environment. |
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