LLC DCM-GALVANI (Elektrougli, Russia)

А. Е. Sinyakov, Deputy General Director for Research and Development

JSC URALINTECH (Yekaterinburg, Russia)

P. S. Potapov, Head of the Laboratory of Hydrometallurgical Processes, p.potapov@pm-ural.com
М. S. Igumnov, External Advisor
А. V. Еrmakov, General Director

The article is devoted to the production and practical application of rhodium electroplating in the jewelry and electronic industries. The main types of electrolytes for rhodium deposition are considered: sulfate, phosphate, mixed, and sulfate-sulfamate systems. Typical compositions of baths for decorative and functional coatings are given, as well as the role of additives: gloss-forming agents, wetting agents and alloying components that allow controlling the microstructure, color and internal stresses of precipitation. Special attention is paid to the effect of impurities on the quality of coatings. Depending on the concentration and nature of the impurity, it can have a critical, neutral, or modifying effect. The methods of electrolyte purification are described: ion exchange sorption, filtration through activated carbon and redeposition of rhodium hydroxide. The importance of raw material control and monitoring of the composition of working solutions is emphasized. Data on the mechanical, optical, and protective characteristics of the coatings are presented: microhardness, internal stresses, crack resistance, color parameters, and corrosion resistance. The factors influencing the formation of defect-free coatings are considered: current density, temperature, acidity and hydrodynamic conditions. Commercial forms of electrolytes are presented: ready-made bases, concentrates, correctors and solutions for electroplating pens. A typical technological process of surface preparation and application of rhodium including degreasing, activation, washing and precipitation is described. The state of the Russian market of rhodium electrolytes is analyzed. It is shown that after the introduction of sanctions, imports decreased but the need for rhodium coatings remains. The solution is to develop our own production facilities based on domestic refined rhodium. It is concluded that rhodium coatings are still in demand due to their unique properties and the absence of equivalent substitutes.

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