Aluminum is a metallic material that is widely used and in high demand among non-ferrous metals, and its applications continue to expand. Products made from aluminum materials are diverse and countless, with statistics indicating over 700,000 varieties. They serve various needs across industries, from construction and decoration to transportation, aerospace, and beyond.

What is Anodizing?

Anodizing refers to the process of forming an oxide film on the anode (aluminum product) by applying an external electric current to aluminum or its alloys in a corresponding electrolyte under specific process conditions.

Why is Anodizing “Highly Favored” in Aluminum Surface Treatment?

The anodizing process for aluminum and its alloys is extensively applied in industry. It is used to prevent corrosion of products or achieve both protective and decorative purposes, such as serving as a wear-resistant layer, electrical insulation layer, primer for painting, or substrate for electroplating.

01 Preventing Corrosion of Aluminum Products

The oxide film obtained through anodizing is inherently stable in the atmosphere, making it suitable as a protective layer. The oxide film produced by anodizing aluminum in a sulfuric acid solution is thick and highly adsorptive. With appropriate sealing treatments, it exhibits excellent corrosion resistance.

02 Protective-Decorative Products

For most aluminum and alloy products requiring surface finishing, anodizing in a sulfuric acid solution after chemical or electrochemical polishing yields a highly transparent oxide film. This film can adsorb various organic and inorganic dyes, resulting in vibrant colors. The colored layer serves both as a corrosion-resistant and decorative coating. Under specific process conditions, a protective and decorative oxide film resembling porcelain in appearance can also be achieved.

03 As a Hard Wear-Resistant Layer

Hard anodizing of aluminum and its alloys produces a thick and hard Al₂O₃ film on the surface. This film exhibits high hardness, significant thickness, and low roughness. Hard and thick oxide films can also be obtained on aluminum products via anodizing in sulfuric or oxalic acid solutions. The porous, thick oxide film can retain lubricants, making it highly effective for aluminum products operating under friction, such as engine cylinders and pistons in automobiles and tractors. Anodizing significantly enhances their wear resistance.

04 As an Electrical Insulation Layer

The oxide film formed on aluminum and its alloys through anodizing exhibits high electrical resistance, contributing to improved insulation for certain products. Anodizing can be used to prepare dielectric layers for capacitors or to create insulating layers on aluminum surfaces.

05 As a Primer for Painting

Due to the porous nature and strong adsorption capacity of the anodized film, it serves as an excellent primer for painting and other organic coatings. It ensures strong adhesion between the paint or organic film and the product, thereby enhancing corrosion resistance.

06 As a Substrate for Electroplating

Before electroplating aluminum and its alloy products, a substrate must be applied. Among the various methods for preparing substrates—such as zinc electroplating, zinc immersion, and electroless nickel plating—anodizing is also a crucial technique.