Corrosion protection usually means applying an additional coating. With aluminum, however, a little oxygen is enough. In the electrolysis process, the metal forms a surface of aluminum oxide that is as hard as it is durable. And it can even be colored.

Text: Stephan Becker

Aluminum is a strange material. On the one hand, not particularly valuable when you think of packaging or old GDR coins. On the other hand, it is hard to imagine many high-tech areas without it. Whether in automotive or aircraft construction, whether for lights or high-end laptops, nothing works without aluminum. This is not least due to its lower density compared to steel. Although it requires more volume to achieve a similar level of strength, it is also significantly lighter.

One disadvantage, however, is its chemical reactivity in addition to the greater energy required to produce it. A natural oxidation layer forms quickly, which in contrast to iron oxide - i.e. rust - already has a certain protective effect. However, as a base metal, aluminum is anything but permanently resistant to corrosion. However, its reactivity can be turned to advantage in the anodizing process.

Anodizing stands for the electrolytic oxidation of aluminium. The principle was invented at the beginning of the last century and popularized under this name by the Vereinigte Aluminium-Werke in Germany from the mid-1920s. Using direct current, a significantly thicker oxide layer is produced in an acidic electrolysis bath. And this is characterized by a dramatically improved hardness and protective effect. This makes anodized surfaces usable and hard-wearing for consumer goods.

Pictures: Markus Bredt; Erdoganlar Aluminum