Eloxing is the name of the process in which aluminium is provided with a protective layer. This process is not a coating of the substrate metal with an additional layer of another metal, but the creation of a protective layer by the aluminium itself. Eloxing is also called eloxal process, which is an abbreviation for electrolytic oxidation of aluminium. In this process, the aluminium is made to form an oxidic protective layer by anodic oxidation. The top metal layer is transformed into an oxide, which protects the layers underneath from corrosion. To ensure that the final surface is even and without cracks, the aluminium must be degreased and pickled before eloxing. This is followed by the actual eloxing process, in which the top layer is coloured and compacted, which is usually done simply with steam or hot water. Eloxing uses electrolysis, where the cathode breaks down oxonium from the acid into water and hydrogen. The anode is the site of oxidation, where aluminium first becomes aluminium-3 ions and then aluminium-3 oxide. Eloxal coatings are used on jewellery to provide a corrosion-resistant surface on a low-cost material. In addition, eloxing is used primarily as corrosion protection for building materials, and this process is also suitable for the automotive industry and for household objects.
