Practice and applications of gold plating
Gold plating of items is the covering of these very items with a layer of gold. This precious metal is not only one of the most corrosion resistant metals, but is also generally considered to be visually very stylish. This makes it perfect for enhancing a wide variety of objects. In addition to gold plating using pure gold, there is also the option of using gold alloys. These can be selected according to the colour, depending on the elements with which the alloy was made.
The following selection is possible:
- Rose gold
- White gold
- Red gold
- Green gold
- Yellow gold
- Blue gold
Furthermore, it is possible to vary the chemical and mechanical properties of gold plating. Its characteristics can be altered by alloying it with different elements, such as cobalt, copper, iron or nickel, to achieve the optimum characteristics for the application in question. Additives such as cobalt, iron and nickel increase hardness and wear resistance. Due to its very good conductivity, gold plating is also used in the electrotechnical industry. Here, plugs, pins, etc. are plated with gold. However, gold also has two disadvantages. On the one hand, it is very rare and therefore much too expensive to produce everyday objects from it in its pure form. Advantages of gilding
For centuries, the gilding of objects has enjoyed great popularity, as it not only enhances them visually, but also provides a high level of protection against corrosion. Gilding increases the longevity of objects and protects them from chemical and mechanical influences. Gilding is mainly applied to metallic objects and those made of metal alloys. But also non-metallic materials, such as ceramics, wood, glass and porcelain, receive a more valuable appearance through a coating of gold or also through gold ornaments. Nowadays, however, various branches of engineering also benefit from the positive properties of gold plating. Gold plating is therefore not only very popular in the jewellery and porcelain industry, but also in electrical engineering, and here in particular in semiconductor technology, where it is highly valued for its positive properties. It has a high bondability and a very low electrical contact resistance. For this reason, it is often used in electrical components such as connectors.
Tradition and modernity of gilding
The craft of a gilder has a long tradition for good reasons. While for centuries it consisted of manually applying gold leaf to various substrates, the process of gilding is nowadays carried out with the help of electroplating technology in particular. The usually metallic objects are dipped into a gold electrolyte and by applying an electrical direct voltage a gold coating is deposited. This is usually done in an electrolytic bath containing an anode and a cathode. The substrate is stored at the cathode, the negative pole. Electric current is now passed through the bath so that dissolved gold metal ions from the cyanide gold bath are deposited on the substrate by the reduction process. In the process of gold plating, a reduction of gold(I) and gold(III) ions from cyanide electrolytes takes place. (The rule of thumb is that the longer the electrolytic bath lasts, the greater the layer thickness). The layer thicknesses can be less than 1µm up to several 100 µm and can be applied as a combination of layers. After the electrolytic bath, the substrate is post-treated, dried and thus remains stain-free. In the meantime, electroplating has almost completely replaced the traditional leaf gilding process, as it is much easier and less cost-intensive to carry out. So the modern age does not stop at this traditional craft.