Semkina O. Improvement of electrochemical deposition of functional copper coatings on alloys of iron and aluminum

The electrochemical processes occurring during the formation of copper coatings on the bases of steel and aluminum alloys are the object of the study. The purpose of the study is to improve the technology of copper electrochemical coatings having high adhesion, uniform distribution on the surface, soldering ability, electro-catalytic properties on the basis of carbon steel and aluminum alloys. Research methods that have been used are the next: potentiometric titration, linear and cyclic voltammetry, chronopotentiation and chronoamperometry, electrochemical impedance spectroscopy, optical and scanning electron microscopy, gravimetry, X-ray diffraction phase analysis. The results obtained include new theoretical assumptions that can be used in the study of copper deposition on bases with more negative values of the electrode potential. The practical value of the work is to improve the electrochemical application of functional copper coatings on the basis of carbon steel and aluminum alloys. The technology that has been developed provides the deposition of coatings with a strong adhesion and a uniform distribution on a basic metal. They can be used both independently and as a sublayer in multilayer coatings, and also allows to increase environmental safety in galvanic production. Novelty is in the scientific basis of the technology of copper depositing from tartrate electrolyte which were created. It became possible to improve the coating process of steel and aluminum alloys. It has been proved that the process of copper reduction from tartrate electrolyte is irreversible, runs through mixed kinetics and includes a rapid preliminary chemical dissociation reaction of the complex ion [Cu(OH)2Tart]2–. It was found that the anode passivation of copper may be due to the formation of its oxide films, conditions for active copper dissolution are determined. It has been determined that with the pH value above 8.5 there is predominantly a complex ion [Cu(OH)2Tart]2- with a low instability constant, which made it possible to develop an electrolyte for depositing copper coatings on the basis having an electrode potential, more electronegative than copper. The influence of the structure and electrical characteristics of oxide films on the surface of aluminum and its alloys on the technological parameters of copper deposition has been revealed. The corrosion resistance of anodized aluminium alloys samples immersed in working electrolyte has been studied, which made it possible to optimize the requirements for the substrate preparation prior to deposition of the coating. Practical implementation also has been provided. The effectiveness of technology proposed has been proven by pilot-industrial tests passed at State Scientific Production Enterprise "Kommunar Corporation" (Kharkiv). The results of the study has been implemented in the educational process of the Department of Technical Electrochemistry of the NTU "KhPI". The scope of application. The results of work can be used in machine-building industry when obtaining functional copper coatings, as well as in higher education institutions for the training of students in technical electrochemistry.