INFLUENCE OF STATIONARY POTENTIAL SHIFT OF ALUMINIUM SURFACE ON PROPERTIES OF NICKEL-PHOSPHORUS COATINGS

The relevance of the research is caused by the need to improve the already known methods of electroless coating deposition. To date, despite numerous studies and practical applications, the process of chemical nickel plating remains imperfect. The low nickel deposition rate, the high consumption of the solution components, and the complexity of the deposition do not contribute to the widespread use of chemical nickel plating. At the same time, chemically deposited coatings are significantly different from the electrochemical: they possess valuable properties. The presented technique of intensification due to the combination of nickel deposition processes by electroless and electrochemical methods is able to increase the deposition rate of the coatings, and also allows influencing their composition and mechanical properties. The main aim of the research is to increase the rate of electroless nickel plating by application of a negative electric potential on aluminium substrate, with a thin layer of chemically predeposited nickel to reduce the time of the process. Objects: nickel coatings on an aluminium substrate made of alloy grade MST. Methods: potentiodynamic, scanning electron microscopy, energy dispersive analysis, microhardness, scratch test, profilometry. Results. Co-deposition of electroless and electrochemical nickel on an aluminium substrate was carried out with the negative electric potential shift. The dependence of phosphorus content in the coatings on the surface stationary potential shift was determined. The physicochemical characteristics of the obtained coatings were studied. It was established that a small shift of the surface stationary potential to the cathode region allows obtaining nickel-phosphorus coatings containing a smaller amount of phosphorus, but superior in properties to an electroless coating.