Egorova L. Physical-chemical regularities of copper and Cu62Zn alloy dissolution in aqueous chloride solutions

Objects of research: copper, Cu62Zn alloy, models and technological solutions of chloride iron(III). The purpose of research: the determination of physical-chemical regularities of chemical and electrochemical dissolution of copper and Cu62Zn alloy in aqueous chloride solutions taking into account complex particles which cause the activation of copper and Cu62Zn alloy dissolution and process by passive superficial phase-forming. Research methods: the method of the rotating disk electrode, the gravimeters, the atomic-absorption spectrometry, the titrimetry, the X-ray analysis, the atomic force microscopy, the electron-probe microanalysis, the methods of polarization measurings. The calculations of distributing diagrams of complex particles by projection method has been done. Theoretical and practical results: The main regularities and macro-kinetic parameters of chemical dissolution of copper and Cu62Zn alloy in concentrated aqueous chloride solutions are defined. It is proved that the diffusion is a limiting stage of the process. Correlations between the anion nature, the type of complex ion and the rate of the process are determined. Complex particles which cause the activation of copper and Cu62Zn alloy dissolution are revealed. The mechanism of the electrochemical ionization of alpha-brass in concentrated chloride solutions is exposed, the limiting of the process by ionization of the copper component in alloy is determined. The activation of brass electrochemical dissolution and disturbance of passivation under the action of chloride ions are proven. It is shown that chemical dissolution of zinc constituent of alloy is facilitated in acid medium. The presence of oxidant ions Fe3+ intensifies active dissolution of brass while preserving the passivation. The composition and modification of passive superficial phase layers on copper and Cu62Zn alloy are determined. The proceeding of grain boundary diffusion of Fe3+ ions in the polycrystalline layer of CuCl is proven. The change of selectivity of brass components chemical dissolution depending on concentration and type of chloride solution addition is determined. The principles of optimization of copper and alpha-brass etching process in chloride solutions are substantiated. The optimal composition of FeCl3 etching solution for Cu62Zn alloy is developedt. The technologically simple, low-waste and resourse-saving methods of regeneration of chloride etching solutions on the basis of FeCl3 and CuCl2 are developed, which allow to solve the ecological problems of technological cycles "Etching - Regeneration". The implementation degree: the results are implemented at SE Ltd. "Mateco" in Kharkiv city and into the academic process at the Chemistry division of Kharkiv national automobile-road university for teaching "Chemistry" and "Methodology of analytical physico-chemical scientific researches in ecology" .