| Zinc deposits have been widely used to protect steel from corrosion. However, with the fast development of technology and modern industry, the demands to the qualities of coatings become more and more strict, the traditional Zinc deposits could not completely meet the requirements. Therefore, many methods have been proposed to improve the corrosion resistance of the Zinc coatings. Among these, electroplated Zinc alloys coatings, as new technologies, come forth as the times require. Zinc alloys coatings possess many beneficial properties, such as excellent corrosion resistance, good ductibility, well painted characteristics, low hydrogen embrittlement, small internal stress, and so on. Therefore Zinc alloys coatings will and must be considered as substitutes for Zinc, Cadmium and Chromium plating, and extensively used in automobile, aviation, apparatus, instrument, construction, electronic industries, and so forth. Overseas, Zinc alloys coatings have been applied, however, in China, these new techniques are virtually at a state of laboratory research. This dissertation based on the current research status, tries to study the electroplating processes and the concerning fundamentals of Zincate Zn-Fe alloy and Zn-Fe-TiO2 composite electroplating, aiming to shorten the gaps between China and the developed countries on Zinc alloys electroplating technique.The main subjects of the dissertation are as follows:The suitable complexing agent of Fe2+ ZFC has been chosen according to the properties of complexer, d electron configuration of metal ions and their acid properties of soft or hard. Based on the effect of brightening on the coatings of the functional group of amine and aldehyde, by making DE as a main brightener and cooperating with appropriate amount of assistant brightener, a Zinc alloy electroplating additives, which has good properties and wide brighter current density region, has been obtained. The results of Hull Cell experimental shows that bright, smooth and fine Zn-Fe coatings could be obtained from the Zn-Fe alloy electrolyte in which the content of ZFA is 50ml L-1 when the cathode current density were in the range of 0.253~3.652A dm-2 at 25C.The process of alkaline zincate Zn-Fe alloy electroplating has been studied. Through the investigation of the alloy electroplating solution ingredients, the process variables and their relationship with the Fe content in the alloy coating, the optimum process has been obtained. It has been found that Zn-Fe alloy electrodeposition belongs to anomalous codeposition. Within certain range, the optical brightness of the coating raise with the increasing of Fe content in the coating, and when the parameters which could effect the optical brightness change, accordingly Fe content in the coating would change. Under the optimum conditions, the anticorrosive and decorative Zn-Fe alloy coating with 0.2%~0.8% Fe has been obtained.For the first time, on the basis of the above optimum Zn-Fe process, the Zn-Fe-TiO2 composite electroplating process has been investigated by using white titanium pigment with an average particle diameter of 0.5 u m. The influence of the composite electroplating solution ingredients and the processABSTRACTvariables on the content of Fe and TiO2 in the Zn-Fe-TiO2 composite coating have been discussed, and the anti-corrosive and decorative Zn-Fe-TiO2 coatings with 0.2%~0.8% and 0.5%~l% TiO2 have been obtained. It has been discovered that the content of Fe and TiO2 in the Zn-Fe-TiO2 composite coating showed obviously cooperative effect.The optimum process of forming a thick anticorrosive black chromate film on a Zn-Fe coating has been obtained. In this process, the phosphatization has been incorporated to increase the thickness of the film, the transition element salt has been used as a blacken agent to take the place of the soluble silver salt, and the suitable additives and assistant film forming agent have been added. The obtained black chromate film has the properties of black and shining, uniform hue, high corrosion resistance, good adhesio...
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