Papers by Keyword: Chromium Plating

Abstract: We considered the processes of chromium plating the inner surfaces of the components of cylinders with hydrostatic guideways. We demonstrated the various aspects of the chromium plating process – the limitations placed on the machinery depending on the dimensions of the parts to be plated and the unevenness of the deposition rate of chromium along the length of the part. We developed a diagram of an installation for the application of a hard chromium coating on inner surfaces, which includes a cathode, an anode, a tank, and a pipeline. The distinctive features of the installation are the method of supplying the electrolyte at an angle to the horizontal, which allows us to supply the electrolyte through a turbulent flow swirling along a helical path, and the use of a chromium-plated installation casing. We studied various modes for applying a hard chromium coating on the inner surfaces of a hydraulic cylinder. As a result, we determined the optimal composition of the chromium electrolyte – the ratio of chromic anhydride and sulfuric acid – which is 10:1, respectively, and experimentally selected deposition modes. Chromium coatings obtained through the use of the concentrated electrolyte, which we developed, and the chromium plating method have 5...20% greater hardness and a 10...30-times reduction in porosity with the formation of a shiny, lumpy sludge, which corresponds to corrosion-resistant and wear-resistant coatings needed to manufacture hydraulic drives with highly efficient hydrostatic guideways.

Abstract: Control rod drive mechanism is one of the key main components in nuclear power plants and serves in harsh environments such as high temperature, high pressure and nuclear radiation. In order to ensure the service life and to prevent biting when assembling, some of the threads of control rod drive mechanism need to be chromium plated. In view of the high demands of the same chromium plating thickness on all surfaces of the threads of control rod drive mechanism of nuclear power and non-uniformity in chromium plating thickness of threads due to poor throwing power of chromium plating solution, five representative kinds of threads of control rod drive mechanism were selected and the plating thickness change of the root diameter, pitch diameter and crest diameter of threads was studied in this paper by means of depositing different thickness chromium coating on the surface of threads. The experimental results show that thicker coating is deposited on the crest of thread because of high current density and thinner coating is deposited on the root of thread because of low current density, which can provide reference for specification of chromium plating thickness of thread products of control rod drive mechanism.

Abstract: The chromium-plating method is proposed to solve the wear and spalling problem of the cold roller in the rolling process. A three-dimensional asymmetric rolling model is constructed by using elastic-plastic finite tool, and the stress on the roller in different plating hardness, thickness and layers in cold rolling process is analyzed. By comparing the simulated results, the optimized state for chromium layer is scheduled.

Abstract: In this study, the production of metallic chromium via metallothermic process was investigated. A chromium oxide-rich residue from chromium plating industry was characterized. Aluminothermic reduction was performed in lab-scale using an open graphite crucible. The plating residue and the aluminum powder were processed in a SPEX mill, in order to promote its effective mixing and mechanical activation. Energy dispersive X-Ray (EDX) analyses in the scanning electron microscope (SEM) have shown the presence of metallic chromium in the reaction products.

Abstract: Decorative chromium demand in the worldwide market is more than three times of hard chromium. But chromium plating processes has long been known to hazardous. The corrosion resistance of a nano-crystalline Sn-Co-X alloy intended as an alternative for decorative chromium has been studied. The corrosion resistance of Sn-Co-X are all better than trivalent chromium, hexavalent chromium, and it is more better than coarser gained Sn-Co alloy. The microstructures of Sn-Co-X alloy were analyzed by SEM, TEM, XPS and AES. The mechanism of its excellent corrosion resistance is described.