Complex Formation and Micropassivation at Electrodeposition of Niobium Coatings in Alkali Chloride-Fluoride Melts With Different Cationic Composition

摘要

The influence of the second coordination sphere complexes on the roughness of niobium coatings was studied. It was determined that due to micropassivation by oxygen impurities as niobium suboxides and oxygen - niobium solid solution the coating roughness in the NaCl - KCl - K_2NbF_7 (8 wt.%) - NaF (10 wt.%) melt diminishes in comparison with CsCl - K_2NbF_7 (8 wt.%) - NaF (10 wt.%) melt. Thus the micropassivation affects on the number of nuclei and the roughness of niobium coatings stronger than complex formation. It was found that pulsed current electrolysis has significant advantages in comparison with direct current electrolysis.