The object to be plated is the cathode (negative electrode). The plating metal is the anode (positive electrode). The electrolyte contains ions of the plating metal.
At the cathode: Metal ions gain electrons and deposit as solid metal on the object. Cu²⁺(aq) + 2e⁻ → Cu(s)
At the anode: The pure metal anode dissolves, replacing ions in solution. Cu(s) → Cu²⁺(aq) + 2e⁻
The electrolyte concentration stays constant because anode dissolution replaces cathode deposition.
Faraday's Law: m = (M × I × t) / (n × F), where F = 96485 C/mol (given in Data Booklet).
Common mistake: Forgetting to convert time to seconds! Always check units.
"Which electrode?" questions: Object = cathode. Pure metal = anode. If you reverse them, plating won't work — the object would dissolve instead.
n value: n is the number of electrons transferred per ion. Cu²⁺ → n=2, Ag⁺ → n=1, Ni²⁺ → n=2, Au³⁺ → n=3.
Chrome plating: Car bumpers and faucets — thin chromium layer for corrosion resistance and aesthetics.
Gold plating: Electronics connectors — thin Au layer prevents oxidation of copper contacts.
Tin plating: Food cans — tin is non-toxic and protects steel from corrosion.
Thickness control: More time or higher current = thicker coating. Industry uses very precise current control for uniform deposition.