In an electrolytic cell, an external power supply forces a
non-spontaneous redox reaction: metal cations in solution are reduced
at the cathode (left) and deposit as solid metal, while the anode
(right, made of the same metal) dissolves to replenish the bath. The
growing gold layer on the cathode is the actual electroplated coating,
scaled up for visibility; blue spheres are metal ions migrating through
the electrolyte toward the cathode.
m = (I·t·M) / (n·F) (Faraday's law of electrolysis)
E_cell = E°_cathode − E°_anode − (RT/nF)·ln(Q) (Nernst equation)
- Plating metal — sets the molar mass and electron count n used by Faraday's law, and the deposit's colour.
- Applied voltage — the driving force pushing current through the cell; more volts, faster deposition (up to a limit).
- Ion concentration — more ions near the cathode support higher sustainable current.
- Plating time — total charge passed, and therefore total mass deposited, scales directly with elapsed time × current.