Refined with electricity

Article of 29 July 2016 

Electroplating is used to refine metal surfaces

Everyone comes into contact with electroplated objects in their life without noticing it: starting with spectacle frames and plug connectors in coffee machines, from chrome-plated taps on the washbasin through to galvanised components in the car. Tools and scissors, for example, are nickel-plated using this technology to protect them against rust.

Electroplating involves refining an object made of an electrically conductive metal by applying a thin layer of a different metal to it with the help of electricity. Electroplating technology enables functional coatings to be applied with a thickness of just a few micrometres and thus to use raw materials in a targeted and efficient manner.

How does electroplating technology work?

Firstly, a workpiece is immersed in a bath made up of a metal salt solution (electrolyte) and connected to the negative electrode of a direct current source (cathode). The metal that is going to be deposited (e.g. nickel) is also placed in the bath and connected to the positive electrode of the direct current source (anode). The electric current dissolves the metal on the positive terminal, which is thus turned into metal ions. These metal ions are attracted by the workpiece on the negative terminal, where they are deposited as a thin metal coat.

In this way, the object being refined is coated evenly on all sides with gold, nickel, silver, copper or another metal. The longer the object is kept in the bath and the higher the electric current, the thicker the layer of metal will be.

Bathing and pickling at the Scharnhausen Technology Plant

Festo also works with this method at the Scharnhausen Technology Plant. In galvanic baths, the components in the products – for example, valve and cylinder housings – are given the necessary properties, such as chemical resistance, hardness, gloss or rust protection, using electrolytic processes. The washed and degreased aluminium parts from the machining department are firstly pickled, whereby a layer of about ten micrometres – which equates to around 0.01 millimetres – is removed. In the anodising process, they are finally given a coating 20 micrometres thick, which protects them from corrosion and ensures a low-friction surface.

When it came to planning the electroplating process at the Technology Plant, attention was paid to energy efficiency. Several components can thus be anodised simultaneously in one tank and no retooling is necessary to change the anodising substances. A heat exchanger enables energy to be recovered from the ventilation system.