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What makes electrolysis or electroplating take so long ? What stage takes longer when ions are attracted to electrodes or when they gain or lose electrons at electrode. And if we are talking about an electrolyte composed of positive ions and electrons , which is faster, electrons entering the circuit at positive electrode or gaining electrons by positive ions at negative electrode?

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    $\begingroup$ 'A watched electrode never plates', as the saying goes. Seriously though, whilst I can't answer the question I would venture that due to dielectric screening, ions in solution only 'feel' the electrodes at very short range, which would imply that electroplating is for the most part diffusion-limited. $\endgroup$ – Richard Terrett Jan 30 '13 at 12:17
  • $\begingroup$ The limiting part is ion diffusion. There is an upper limit to voltage applied, or wrong ion will be reduced, and with that the speed of diffusion is limiting stage. $\endgroup$ – permeakra Feb 4 '13 at 7:26
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It depends: The rate of electrolysis is limited either by the electric source or by the ion concentration. I am inexperienced with electrolysis but I imagine that quality may increase as the the process slows, much like crystals grow with more imperfections when the rate of crystallization is fast.

There is no such thing as an electrolyte solution composed of positive ions and electrons.

"Activity coefficients of single ions cannot be measured experimentally because an electrolyte solution must contain both positively charged ions and negatively charged ions." -Debye–Hückel theory

Electroplating systems tend to use an electrode source that replenishes the solvent ions plated onto the target electrode.

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