Aluminium (Al) anodizing, or anodic oxidation coating on aluminium, is a processof electrolytic treatment of aluminium. Anodizing is used to increase the thickness of the natural oxide layer on the surface of metal partsin order to improve their corrosion and wear resistance. As such, anodizing is rather popular, yet the quality of the coatings and their properties depend on many factors. To a large extent, the quality depends on technical equipment and technological processes as well as on the quality of the chemical substances. However, the competence of the staff are no less important.
UAB "Alanodas" is a joint-stock company working in partnership with an open access Centre for Chemical Conversion Coatings which was established in the Center for Physical Sciences and Technology . The company continues to develop the processes of surface coatings of the aluminium and its alloys, the activity that was launched in the Centre in 2002.
Aluminium anodizing is performed using chemicals of highest quality, all technological processes are designed, carried out, controlled and tested by specialists and scientists of supreme qualification. The staff of UAB "Alanodas" are professionals with a long-standing experience.
Technological processes employed
- Type II coatings (ISO 7599:2010, MIL-A-8625F)are the result of electrolytic treatment of aluminium in a bath containing sulphuric acid. During this process a porous (diameter of the pores is 50–200nm), 6–25µm thick coating of aluminium oxide is produced on the metal surface.
- Type III coatings (ISO 10074:1994,MIL-A-8625F) are the result of electrolytic treatment of aluminium in a bath containing a mixture of sulphuric and oxalic acids at low temperatures (0–15°C). During this process a heavy coating of 10–150µm thickness is produced, characterized by especially high corrosion and wear resistance and good electrical insulation properties.
Anodic coatingsmay be clear (Class 1) and dyed or pigmented (Class 2). In Class 1, any natural coloration of the coating is the result of the composition of the aluminium alloy from which the anodized parts are produced. In Class 2 the colour of the coating is the result of exposure to a solution of a suitable dye or stain, filling the pores of the coating being formed.
Chrome free passivation of aluminium and its alloys
Process (chrome free Conversion Coating for Aluminium Immersion Application) meets the requirements of RoHS, ELV and WEEE directives. It is used as an anti-corrosive film before dyeing (Class 1 of conversion coatings) and as an electrically conductive anticorrosive coating (Class 3).
Chemical steel passivation
The process is used to increase the corrosion resistance of ferritic, martensitic (AISI Type 4XX), austenitic (AISI Type 3XX) alloys and stainless steel with >17% of chromium or chromium and carbon content (Series 440).