Electroplating deposits a metal layer onto a part by making the part the cathode in an electrolyte containing salts of the metal you want to deposit. That's the physics. The engineering is in everything that happens before and after the current is switched on.
The four stages
- Pretreatment. Degreasing, then pickling or descaling, then activation. This determines adhesion. Nothing you do later compensates for skipping it.
- Plating. The part is the cathode. Deposition rate and uniformity depend on bath chemistry, temperature, current density, and how the part is presented to the anodes.
- Post-treatment. Rinsing, and where applicable passivation or sealing.
- Inspection. Appearance, coating thickness, adhesion, salt spray.
Four ways to present a part to the bath
| Method | Best for | Trade-off |
|---|---|---|
| Rack plating | Larger parts, baskets, anything with critical appearance | Each part is individually racked, so labor is higher and throughput is lower, but you control the deposit |
| Barrel plating | Small parts in volume: fasteners, small stampings | High throughput and low cost, but parts tumble against each other and appearance is less controlled |
| Continuous plating | Wire and strip | Very efficient for a continuous feedstock, useless for discrete parts |
| Brush plating | Local repair, touch-up | Manual, flexible, not a production process |
What actually determines quality
In our experience, in order: how thorough the pretreatment is; whether racking and current density are matched to the part geometry; bath chemistry and temperature control; and whether anyone is actually inspecting the output. The first two account for most defects we see on parts that come to us from another shop.
FAQ
Why does plating peel?
Almost always incomplete pretreatment or insufficient activation, both of which mean poor adhesion. See why plating peels.
What method for small parts in volume?
Barrel plating.
What method for complex wire baskets?
Rack plating, which is what we use for wire mesh work. Request a quote.