• June 21, 2024
  • Shatou, Changan, Dongguan, CN
anodizing color

What is anodizing and how does it work?

Anodizing is a surface treatment technique that enhances the corrosion resistance, hardness, and adhesion of metal while also improving its appearance through the formation of an oxide layer on its surface.

During the anodizing process, the metal part is typically used as the anode. It is immersed in an acidic solution containing an electrolyte, while the cathode is usually made of lead or aluminum plate. Under the influence of an applied current, the surface of the anode metal is oxidized to form an oxide film.

In this article, we will explain how anodizing works and the characteristics of the oxide film.

Specific working principle

The process of anodizing mainly includes three steps: pretreatment, electrolyte, and electrolysis process.

1. Pretreatment

First, the metal surface must be cleaned to remove surface pollutants and oxides to ensure the accuracy and stability of the anodizing process. Commonly used pre-treatment methods include alkali washing, pickling, and annealing.

2. Electrolyte

The electrolyte is an essential component of the anodizing process and usually comprises a solution containing acidic or alkaline elements. The acid or base in the electrolyte will ionize, creating a solution that corrodes the metal surface or forms a thin oxide layer.

3. Electrolysis process

In the electrolyte, the metal to be treated is made into an anode, and the corresponding cathode (usually made of aluminum) is connected to the power supply to form a set of batteries. When an external voltage is applied, an oxidation reaction occurs on the anode to oxidize the metal surface. During this process, the metal ions present on the surface of the anode are oxidized into metal oxides, and this results in the formation of a dense oxide layer, known as an oxide film, formed on the metal surface.

Characteristics of the formed oxide film

The oxide film formed after anodic oxidation has the following characteristics.

1. High hardness

The hardness of the oxide film can reach 200-500HV, much higher than the hardness of the base material.

2. Strong corrosion resistance

The oxide film has good corrosion resistance and can maintain its stability under strong chemical corrosion conditions such as acid and alkali.

3. Good insulation

The oxide film has good insulation properties, which can isolate current to a certain extent and reduce current loss.

4. High surface finish

The oxide film has a good surface finish and can show different colors, which increases the decoration of the metal surface.


Anodizing is widely used for surface treatment of metal products such as aluminum, magnesium, and titanium alloys to improve their resistance to corrosion, strength, and appearance quality. It is commonly utilized in industries such as electronics, aerospace, construction, and automotive.

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