Electrodeposition: the plating process step by step

When a client asks "how does the gold actually stick to the piece?", most resellers answer "it is plated". And stop. That answer does not sell. What sells is opening a little window into the factory and showing, in three sentences, how the gold gets there. Whoever understands the process defends the price without sweating. This lesson is your factory floor in eight minutes.

The piece before it becomes jewelry

It all starts with a finished piece in brass (or in hypoallergenic alloy, for our sensitive-skin lines — you saw this in lesson 3 of module 1). It already has the final design, polished, sanded, no burrs. But it is a naked piece. Gray, dull, no identity yet.

Before any plating, it goes through a sequence nobody sees and that defines everything: degreasing (removes oil from the hands and machines that touched it), pickling (a light chemical attack that opens the metal's pores), activation (leaves the surface chemically hungry to receive the next metal). If any of those steps fails, the plating still sticks — but peels in a few months. That is why lesson 4 of this module, on why plating peels, starts exactly here.

The tank, the current, the gold in suspension

Then comes the heart of the process: the piece is dipped in a solution with 18k gold ions in suspension. On one side of the tank, a positive pole (anode). On the other side, the piece (cathode). The current is turned on.

The parameters the factory controls, every day, in every batch:

Voltage between two and four volts. Too little does not pull the gold; too much burns the piece.
Current density between one and five amperes per square decimeter. That is what sets the deposition speed.
Temperature between forty and sixty degrees Celsius. Cold bath is thick and poorly bonded; too hot wastes gold to evaporation.
Time of ten to thirty minutes per layer, depending on the desired thickness.

The gold ions travel, pulled by the current, until they reach the piece. There they anchor atom by atom on the surface. It is not paint. It is not glue. It is real chemical deposition. Real 18k gold becoming part of the piece.

Why several layers, not just one

Here is the detail that separates Herreira from the half-micron plating of the mass market. In a quality piece, the process is not a single bath. It is a sequence:

Nickel or barrier bath (in alloys that allow it), which creates an even floor.
Intermediate bath (copper, in some cases), which adds adhesion.
Main 18k bath, in a thick layer.
Protection bath (rhodium on white pieces, protective varnish on yellow), which seals the finish.

On hypoallergenic pieces Herreira skips the nickel and uses alternative barriers — expensive, but that is what guarantees the no-allergy line, exactly like I explained in lesson 3 of module 1.

Why this matters for the sale

Your client does not need to memorize volts and amps. But she needs to feel that you know. When you say "the plating is done by electric current in layers, controlling temperature and time, so each piece gets the same gold thickness", you speak with the authority of someone who has seen the tank. And that changes the game.

Pocket sentence

"18k plating is not paint — it is gold deposited by electric current, atom by atom, in layers controlled by the factory."

What to practice this week

Take a Herreira piece of yours and, in front of the mirror, narrate out loud its journey from brass to vitrine: degreasing, pickling, activation, intermediate bath, 18k bath, protection. Do it in under a minute. Repeat until it becomes table talk, not recitation. On the next sale, slip in two of those steps — just two — when the client picks up the piece.