Yellow chromating - yellow zincing

Yellow zinc coating, as it is colloquially known, does not exist as a separate process. Instead, a pure zinc coating is first applied to the metal, which has a silvery-white colour and protects the metal from corrosion. This is followed by chromating, which gives the surface its characteristic yellowish to golden colour. This chromating not only serves to improve corrosion protection, but also gives the component a decorative appearance.

The yellowish colour is created by a chemical post-treatment of the zinc coating, known as chromating or yellow chromating. This process is often used in electroplating to enhance the appearance of components and increase their corrosion protection. Typical areas of application for yellow galvanised surfaces are the automotive industry, construction and electrical engineering.

In the past, however, these coatings were based on chromium VI, which was both harmful to the environment and highly toxic to humans. Chromium VI could leach out of the coating over time, leading to serious health risks. For this reason, such coatings are now banned.

In recent years, intensive research has been carried out to develop a chromium VI-free yellow iridescent coating. There are now solutions based on chromium III that can produce a similar yellowish coating. These new coatings are visually similar to the original, but they are not quite as intensely yellow and iridescent as the old chrome VI coatings. The corrosion protection of these new coatings also does not quite reach the level of the earlier coatings, but is already at a high level.

However, it is not easy to reproduce high-quality yellow galvanising in the hobby cellar. High-quality yellow chromates in particular are difficult to achieve. We are also working intensively on a solution to develop a high-quality yellow chromate coating, but have not yet achieved a satisfactory result.

What alternatives are there?

Due to the restrictions on chromium VI, the automotive industry is now increasingly focussing on zinc-nickel coatings. These offer excellent corrosion protection thanks to their combination of zinc and nickel and are used particularly in areas that are at high risk of corrosion.

If you would like to find out more about zinc-nickel, you can read about it here: Zinc-nickel