The discussion on environmental and climate protection became one of the key drivers in the field of research and development. As a result, lightweight design is becoming increasingly important for saving energy and resources, especially in engineering and construction. In addition to plastics, which often fail in terms of strength and thermal stability, light metals such as titanium, aluminum and magnesium are enjoying growing popularity. In order to meet the high demands of the various application areas, e.g. aerospace, automotive or implant industries, these materials require both functional and decorative surfaces as well as resistant and corrosion-proof protection layers.

A special advantage of the light metals mentioned is their natural characteristic to get coated by a protective oxide layer passivating the surface. For the first time, H. Buff observed this feature for aluminum in 1857 and laid a decisive foundation to establish the industrial procedure.

The process of converting a metal surface into its metal oxides and hydroxides forced by application of an external current flow is called anodic oxidation. The component used as an anode is connected to a conductive, normally aqueous solution (electrolyte) and an inert, unchangeable cathode forming a closed electric circuit. The passive protective layers generated by this process can reach thicknesses of a few nanometers (natural oxide layer for aluminum is about 1.5–5 nm) up to several micrometers, e.g. hard anodized up to 250 µm, and convince with a very good adhesion.