Study On Trivalent Chromium Plating Process And Properties Of Chromium Layer

ABSTRACTIt's urgent to develop the technique of trivalent chromium plating because of the heavy pollution of hexavalent chromium plating. The plating technique of trivalent chromium used now has many disadvantages such as low stability of solution, high cost of raw material. For the time being, there is still no perfect trivalent chromium plating technique having been used in industry in China. Thus the research on trivalent chromium plating attracts many concerns.In this paper, the preparation of the source of chromium was explored. I lull cell test was used to have the research on the prescription of trivalent chromium plating solution by single factor test and orthogonal test. The compositions and concentrations of main conductivity salt, complexing agent, wetting agent and special additive, as well as how they affect the quality and performance of deposited layer were determined. The technological process of trivalent chromium plating and the way of preparing the cheap chromium material were explored. The contribution of the technological parameter, such as current density, temperature, pH values and time to the trivalent chromium plating, was studied. The technological condition, which is suitable to be industrialized, was determined.For the purpose of industrial manufacture, the practical and comprehensive system of evaluation criterion was made for the chromium electrodeposited coating's physical and chemical properties. Besides, through parallel analysis, the indexes of trivalent chromium and hexavalent chromium electrodeposited coating were contrasted. Seen from the experiment result, it is clear that the deposited coating obtained with the trivalent chromium electrodepositing method we use is smooth, homogeneous, dense, and has good unti-erosive ability, high stiffness. Thecolor ol ihe deposited coaling ol irivalent chromium is similar with that of hexavalent chromium. Further more, this process has a good ability of homogeneous and deep depositing with simple facility, high current efficiency, and wide working current flow and even more it avoids environmental pollution.In the research on the physical and chemical properties of chromium, AFM was first used to explore the effect of technological conduction to the topography of coating deposited, the size of crystal grain and the regularity of the growth of crystal grain. With the combination of XRF and XRD, we studied the rule of component, structure, crystal grain feature of chromium deposited coating. The law of trivalent chromium electrodepositing were extracted and contrasted with that of hexavalent chromium, laying a foundation stone for the deeper research on the process of trivalent chromium electrodeposition and it's industrialization.