What is anodizing?

Characteristics of aluminum base material

Advantages
Light and strong	With a specific gravity of 2.7, one-third that of iron, it is used in aircraft parts due to the enhanced strength achieved through alloying.
Good heat conductor	Its thermal conductivity is three times higher than iron, making it ideal for automobile radiators and heat exchangers.
good electrical conductor	It can carry double the current compared to copper of equivalent weight. Its lightweight nature makes it a candidate for power transmission lines.
rust resistant	A very dense oxide film forms on the surface, which acts as a protective layer and prevents corrosion.

Disadvantages
Difficult to weld	The oxide film has a high melting point of about 2000°C, requiring its removal prior to welding. Additionally, the base material's thermal conductivity affects the welding process.
Has a large thermal　expansion coefficient	The linear expansion coefficient is about twice that of iron-based materials, so there is a risk of damage due to thermal fatigue.
Difficult to paint	The oxide film on the surface is chemically stable, making it difficult to apply general paint.
Corrodes depending on conditions	Corrosion leading to destruction occurs in alkaline or acidic environments and in contact with dissimilar metals.

►A method to improve the shortcomings of aluminum

Difference from plating

Different ①

Whereas plating is simply a film that builds up on the base material, anodizing penetrates the base material and forms a film, producing a durable coating.

Different ②

Anodizing forms a metal film using the anode, while plating uses the cathode in a water tank.

Anodized surface treatment

Plating treatment

►Processing image

►Differences in film formation

The film penetrates from the surface of the aluminum base material to the inside, and at the same time grows on the outside. This is a treatment that is suitable for expressing the unevenness of the material.

►Differences in film formation

Used when processing metals that are less susceptible to corrosion due to oxidation, unlike aluminum. It differs from anodizing in that the plating layer does not penetrate the base material.

Difference from chemical coating

Different ①

Chemical coating involves submerging metal in an acidic or alkaline solution without using electricity. This method produces a chemical layer that enhances rust prevention and facilitates subsequent painting.

Different ②

Chromium is used to treat metals such as steel, zinc, and aluminum due to its hardness and corrosion resistance.

Types and characteristics of anodizing