Astor Company Profile

what is electroplating?

HOW IS IT DONE?

Electroplating is not simply a matter of 'dipping a part into a bath of metal'. Just as with painting a wall, the preparation is as critical as the final operation. The processes undertaken in plating are as follows.

1. The first step is cleaning to remove any grease or oils from the surface. Often with steel or copper alloys there will be a black scale which needs removing prior to polishing. Some steel components come to us with a zinc coating (Zincseal for example) again this is removed in an acid bath prior to polishing. Where the component has previously been plated this will need to be removed electrolytically (this is the reverse of plating).

2. In most cases polishing is required prior to plating. Polishing is a most critical stage in the process, and in almost all cases is the determinant of the final quality of the finish. Plating will show up any marks present in the original material and in fact because of the highly reflective metal finishes applied, often the marks are even more visible.

Polishing requires a series of stages to remove the marks left by each prior step. In almost all cases where a high quality decorative finish is wanted, the first step is to use a course grinding belt to take off the surface layer. This is followed by the use of progressively finer belts then followed by the use of polishing or buffing wheels using fine cutting compound to produce a mirror like finish. Typically three to five stages are involved to produce a finish suitable for the next step which is electroplating.

3. After polishing the component will have on the surface a mixture of cutting or polishing compound and various greases. This needs to be removed as the metal surface must be microscopically clean prior to electroplating. This is done in a series of cleaning baths, Mostly these contain strong detergents in an alkaline solution.

4. Then the parts are electroplated with a copper coat (for adherence) followed by nickel plating to a thickness of approximately 15 to 25 microns. It is the nickel plating which does the real work. Nickel is highly corrosion resistant (it gives stainless steel its protection). Nickel also gives a bright shiny appearance to the component and it levels out the hills and valleys on a microscopic scale.

Stages 5 - 7 concern the application of a decorative coating. This is relatively thin and is really there for final appearance.

For example: Brass

Brass

5. Immediately following the nickel plating comes plating of a brass coating of I or 2 microns. This coating is a mixture of copper and zinc which are the metals which make up the alloy of brass.

6. The final step is to rinse the part thoroughly then to dry prior to applying a protective coating.

7. The protective coating is a wet sprayed two pack polyurethane (Dulux) which is cured at 130 degrees C. Typically this coating is around 15 microns thick.