Metal anodization is a well-known process in many industries, yet it often remains unclear in its details. This article aims to answer all your questions and clarify any doubts about the topic.
Anodization: The Oxidation Process that Protects Metals
Anodization, or anodic oxidation, is an electrochemical process typically applied to aluminum. This process creates a protective layer on the aluminum surface, enhancing its corrosion resistance. Used in various sectors, from industry to domestic applications, anodization is an essential treatment for improving the durability and appearance of aluminum components. Anodization processes must comply with various regulations (e.g., ISO 7599:2018, EN 12373, and UNI 10681:1999) to ensure quality and adherence to industrial standards. It is versatile and can be applied to different aluminum alloys, including extruded and rolled aluminum (2011, 11S, 6060, 6082, 7075, Ergal, Anticorodal) and aluminum used in low-pressure and shell casting.
Stages of the Anodization Process
The anodization process is divided into three main stages: pre-treatment, anodic oxidation, and sealing. If the piece is to be colored, a coloring phase can be added before sealing.
- Pre-Treatment: Before oxidation, the piece’s surface must be cleaned of dust and grease. Thermal treatments such as hot bending or welding can cause alterations that affect the anodized layer. These irregularities are removed through chemical etching to obtain a homogeneous surface.
- Anodic Oxidation: The aluminum piece is immersed in oxalic or sulfuric acid and connected to the positive pole of a direct current generator, creating an anodic circuit. A cathode, usually made of titanium or lead, is unaffected by the electrolyte. During the process, water splits into hydrogen and oxygen. The oxygen reacts with the aluminum, forming a barrier layer that penetrates the metal, creating capillary-like pores.
- Coloring: After oxidation, acid residues are removed, and the piece can be immersed in a dye bath. The open pores absorb the dye, protecting the piece from abrasion. Common colors include gold, purple, blue, red, green, and black, but white cannot be achieved.
- Sealing: Finally, the piece is boiled in demineralized water, forming transparent aluminum hydroxide that seals the remaining pores, completing the anodization process.
Benefits of Anodization
Anodization offers numerous benefits for aluminum components:
- High corrosion resistance: Ideal for outdoor use.
- Hard and scratch-resistant surface: Ensures durability and resistance without flaking.
- Decorative properties: Allows for a wide range of colors.
- Thin layer: Does not significantly alter the piece’s dimensions.
- Electrical insulation: Improves material safety.
Conclusion
Metal anodization is crucial for preventing corrosion and abrasion, enhancing material hardness, and providing long-lasting thermal insulation. Moreover, it allows for aesthetically enriching the metal with a wide range of colors, making it more robust and visually appealing.
Panotec Metalworking, with a trusted network of external suppliers, offers a complete range of treatments including galvanization, anodization, nickel plating, bluing, and others. These treatments aim to improve corrosion resistance, hardness, wear resistance, aesthetic appearance, as well as the functional properties and machinability of metal components.
