RESEARCH OF THE INFLUENCE OF GLYCIN ADDITIVES ON THE COMPOSITION AND STRUCTURE OF ZINC-NICKEL COATINGS DEPOSITED FROM A SLIGHTLY ACIDIC ELECTROLYTE ON BRASS GRADE L65
DOI:
https://doi.org/10.14529/met200306Keywords:
zinc, nickel, alloy, electrolysis, co-precipitation, electrolyte, coatingAbstract
Now, coatings with various electrolytic alloys are in great demand in the industry due to their unique properties that is different for coatings with pure metals. Zinc Nickel coatings are electrolytic coatings and having a number of high performance properties, can serve as a replacement for toxic metals coatings, such as cadmium. Nevertheless, the use of these coatings is restricted because of the complexity of electrodeposition processes. In this paper, the influence of glycine additives on the composition and structure of Zinc-Nickel coatings, as well as on the current output due to a decrease in hydrogen production, is investigated. Two types of electrolyte are used in the research; the chemical composition of electrolytes was controlled by bichromatometric and complexometric titration methods. The chemical composition of electrolyte was determined using a scanning electron microscope JEOL JSM-6460LV. In the whole range of operating current densities, during deposition from both electrolytes, it was found that zinc, being a less noble metal, is precipitated more preferably than Nickel. This process is called “abnormal co-deposition”. The analysis of microphotographs of the deposited coating surfaces showed that at low current densities the grains have a rounded shape, and at high ones they are faceted, and crystal-like surfaces are formed. The addition of glycine to electrolyte allowed increasing the range of operating current densities. The deposition rate of the coating components and the growth of its thickness are similar to the results of deposition in electrolyte. However, the Nickel content increases due to the formation of electrochemical active complexes of Nickel with glycine on the Nickel anode. In addition, the coatings deposited from electrolyte have increased decorative properties due to the fact that glycine lowers the yield of hydrogen on the surface of deposited plates, and the coatings are obtained with the least number of defects.References
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