Study On High Performance Compound Additives For Chromium Electroplating

Using contrast and orthogonal experiment methods ,the effect of electrolyte formulae for varied concentration of Cr03 and technology of chromium plating on coating property was studied systematically in this paper . Primary factors and their interrelations,which influence the brightness of coating,the current efficiency,dispersion ability and sedimentation velocity of electrolyte were discovered. This has biggish practical significance in improving electroplating quality,saving electric energy and alleviating environmental pollution.It was pointed with the experiment methods of electro-chemistry,metallographic analysis,weighing,spot count and bending that:the additives play an important part in getting high quality coating. However,the effect of different kinds of additives on performance of electrolyte and coating and the part of same additive in different electrolyte are varied. Each additive is selective to electrolyte. The acting effect of organic additives is better than that of inorganic ones. The suitable additives recombination can not only improve considerably the quality of chromium coating,increase the brightness,current efficiency,dispersion ability and sedimentation velocity,but also enlarge the application scope of chromium plating technology. The action of composite of purely inorganic additives on improving coating quality is worse than that of composite of purely organic and organic and inorganic additives. The rare earth has a notable effect on coating quality. Especially under the high temperature and medium current density,it can strikingly improve the integrated properties of coating. The recombination of rare earth with organic additive can make up for the weak of single addition of rare earth. This achievement lays theoretical basis for the development of compound additives.The action effect of compound additives is not the simple superpositionof single additive,but each factor promotes and conditions each other. The action mechanism of compound additives is mainly the composite of the following three aspects:a. To change the surface condition of electrode and the potential distribution of boundary layer through adsorption,thus affecting the electrode process;b. To produce the "effect" by changing the structure of electric double layer and influence the surface concentration of reaction particle and activation energy of interface reaction,thus affecting the speed of electrode reaction;c. To influence the composition and the permutation mode of reaction particle on the interface and the reaction speed of interface by complex action,thus preventing the metal ion from discharging and improving the cathode polarization. The result provides theoretical basis for study on action mechanism of galvanization additives.The optimum formulae of TJ1-TJ7 of compound additives for chromium plating which are suitable to low,medium and high concentration of CrO3 respectively were obtained on the basis of multitude experiments. The formulae that didn' t contain fluorine had low rates of corrosion,high stability and easy operation and had distinct improvement in coating quality,surplus of chromium,saving electricity and energy and environmental protection etc. When they were compared with the commercial additive of WR-1 and the electrolyte formula of FengHui galvanization plant,the results showed that the effect of chromium plating of the formulae obtained in this study are more excellent. As a result,the compound additives for chromium plating studied in this paper has biggish application prospect.