Experience and Perspectives of Electrodeposition from Electrolytes-Colloids of Nickel Plating

Abstract

The investigation and use of colloid-electrolyte baths from the time of first, publications had proceeded mainly in the field of working out highly efficient baths with low concentrations of electrolytes in connection with acute ecological necessity, saving energy and profit. We call briefly colloid-electrolytes such plating baths, where metal deposits are formed by reducing not only metal ions but also colloids and fine dispersions of this metal compounds. This dispersions in the field of the cathode (in the part of diffusion layer where the rate of stirring usually tends to zero) may be treated in certain optimal cases as the systems of mobile pores, giving rise to electrokinetic phenomena, equilibrium and nonequilibrium and thus to efficient stirring this part of diffusion layer, difficulties of the electrochemically reacting species transfer through which are the main obstacle for the cathode processes intensification. It results in reducing or eliminating the diffusion control and gives the essential rise of the limiting current densities. There was observed in some cases for chloride colloid electrolytes the correlation between decrease of polarization in comparison with conventional baths and degree of operating current densities increase. In chloride solutions colloids and fine dispersions, especially protected ones, are more stable than in solutions, where multi charged anions prevail. The polarization's decrease in chloride electrolytes was investigated also. We tend to explain the referred to phenomena by lessening the diffusion control in presence of mobile pore's systems of reducing to metal at the cathode colloids and fine dispersions of that metal's compounds.

Electrodeposition kinetics and surface morphology of Ni-B-UDD composite coating

“…A current efficiency of more than 100% is the most important characteristic of electrolytes containing fine particles (both introduced into the electrolyte and formed during electrolysis) involved in electrode processes [7]. Figure 1a shows the dependences of the current efficiency of (1) nickel and (2) hydrogen on the electrode potential in the electrolyte of the optimal composition for obtaining a wear-resistant nickel-boron-UDD ECC at pH 3, but in the absence of DHBN and UDD additives.…”

“…Bulk nanocrystalline Ni-B alloys exhibit good ductility in tensile loading. The intensification of the processes of metal electrodeposition from colloidal electrolytes has been theoretically and experimentally substantiated [7].…”

The effect of nano-additives on the processes of electrodeposition of nickel precipitation

“…The most commonly used protective deposit in industry is nickel. There are following directions of obtaining deposits containing a dispersed phase: deposits from suspension electrolytes obtained by the electrochemical method and containing the dispersed phase artificially introduced into the electrolyte; electrochemical deposits of electrolytes forming a dispersed phase during its preparation or electrolysis (also named colloid electrolytes) [1][2][3].…”

Ultra-Dispersed Additives in the Nickel Colloid-Electrolyte Baths

“…Наиболее используемым в промышленности функциональным покрытием является никель. Сложились следующие направления получения покрытий, содержащих дисперсную фазу: покрытия из электролитов-суспензий, получаемые электрохимическим способом и содержащие искусственно введенную в электролит дисперсную фазу; электрохимические покрытия из электролитов, образующих дисперсную фазу в процессе его приготовления или электролиза (электролиты-коллоиды) [1][2][3].…”

“…Превышение выхода по току никеля 100% является отличительной особенностью электролитов-коллоидов никелирования, особенно при малых плотностях тока, когда для полного восстановления полидисперсных частиц коллоидов и тонких взвесей восстанавливающегося на катоде металла поляризация не достигает необходимой величины. При этом возможно получение качественных покрытий [2][3]. В нашем случае, такие аномальные значения выхода по току выше 100% наблюдаются в электролите, содержащем УДА (кривая 4).…”