A Complete Guide to Anodizing Aluminum

Entering a new era of the digital industry, creating high-quality, durable, and aesthetically pleasing metal parts is what cnc machining manufacturers pursue. For aluminum parts manufacturers, aluminum parts products must take into account both excellent mechanical properties and aesthetic design, so the anodizing aluminum process is a good choice for parts processing.

parts processed by aluminum anodizing manufactured by YIJIN Hardware

Because the metal components are subjected to anodizing aluminum treatment, the oxide film formed on the surface of the machined parts has good protection, decoration, and other characteristics. Therefore, the technology of anodizing aluminum is widely used in aviation, electrical appliances, electronics, machinery manufacturing, and the light industry.

What are the benefits of anodizing aluminum? What are the uses of anodizing aluminum treatment, and aluminum alloy anodizing? YIJIN Hardware is here to share.

What Is Anodizing?

Anodic oxidation is the electrochemical oxidation of metals or alloys. Under the corresponding electrolyte and specific process conditions, aluminum and its alloys form an oxide film on the aluminum product (anode) due to the action of the applied current.

Anodizing usually refers to sulfuric acid anodizing unless otherwise specified. Anodizing surface treatment technology is to overcome the defects of aluminum alloy surface hardness, wear resistance, etc., expand the scope of application, and prolong the service life of iron components. It is also the most successful surface treatment technology at present.

aluminum parts processed by powder coating manufactured by YIJIN Hardware

What Is Anodizing Aluminum?

Anodizing aluminum: A material protection technology in which an oxide film is formed on the surface of metal material in an electrolyte solution by applying an anode current. Also known as surface anodizing.

After the metal material or product is anodized on the surface, its corrosion resistance, hardness, wear resistance, insulation, and heat resistance are greatly improved.

The most anodized metal material is aluminum. The anodization of aluminum is generally carried out in an acidic electrolyte, with aluminum as the anode.

anodize aluminum parts manufactured by YIJIN Hardware

During the electrolysis process, the anion of oxygen interacts with aluminum to produce an oxide film. This kind of film is not dense enough when it is first formed.

Although it has a certain resistance, the negative oxygen ions in the electrolyte can still reach the outer layer of the aluminum and continue to form an oxide film. As the film thickness increases, the resistance also increases, and thus the electrolysis current decreases. At this time, the outer oxide film in contact with the electrolyte is chemically dissolved.

Aluminum Anodizing stainless steel material

When the rate of oxide formation on the aluminum surface is gradually balanced with the rate of a chemical dissolution, the oxide film can reach the maximum thickness under this electrolytic parameter.

The outer layer of the anodized film of aluminum is porous, and it is easy to absorb dyes and colored substances, so it can be dyed and improve its decoration. After the oxide film is sealed with hot water, high-temperature steam, or nickel salt, its wear resistance can be further improved.

The Benefits Of Anodizing Aluminum Parts

Anodized aluminum parts can improve the corrosion resistance of the component and prolong the service life of the workpiece.

The most in-depth analysis of the benefits of anodized aluminum is its excellent workpiece surface protection function. Aluminum parts are easily affected by the natural climate, which can cause corrosion.

Anodizing, on the other hand, creates a thick protective film on aluminum products. The anodizing aluminum process can increase the aesthetics, and durability of metal components.

type ii anodizing parts manufactured by yijin hardware

Anodizing aluminum used in natural environments today is higher than metal parts used in non-natural environments.

Anodized aluminum for improved wear resistance of aluminum parts.

Aluminum parts are particularly susceptible to scratches and wear, and anodized aluminum products have a very hard surface, with an aluminum oxide film hardness up to HV300. The abrasion resistance is improved, and it is not easy to be scratched.

Anodized Aluminum for Improved Performance and Appearance of Aluminum Parts

Regarding the anodizing aluminum process, the performance and appearance of processed aluminum parts are the focus of many customers. Anodizing Aluminum can improve the appearance and performance of the parts, and can make glue and paint primer surfaces have excellent adhesion.

Of course, starting from the appearance of aluminum parts, anodizing aluminum technology will produce an anodized film on the external of the aluminum products, making the painting more uniform and beautiful.

anodized parts manufactured by yijin hardware

After the metal parts are subjected to anodizing aluminum, the quality of the external protective film can be judged by tests such as friction, electrical conductivity, and electric shock.

At present, the process of the anodizing process still continues the tradition, including degreasing, water washing, anode reaction, water washing, sealing, and finally high-temperature baking.

Anodizing can be applied not only to aluminum but also to other metals such as zinc, magnesium, and titanium.

Anodized Aluminum Parts for Easy Recycling

One thing that is really hard to know about the advantages of aluminum anodizing is that it is easy to recycle. Metal parts are regularly reported for loss, depreciation, and recycling, which are of great concern to parts manufacturers.

aluminum parts through anodizing process

Anodizing Aluminum Process

Precautions for the Process of Anodizing Aluminum and Coloring

Anodizing coloring is one of the most common processes in aluminum oxidation treatment. It can bring excellent acid to create decoration function to aluminum products. So what should be paid attention to in the process of aluminum anodizing coloring and before and after?

Do A Good Job of Cleaning After Coloring

If the surface of the aluminum parts is not cleaned, the residual color paste will affect the aluminum products.

Pay Attention to Cleaning Before Coloring

Since the anodizing treatment tank needs to be fully cleaned after taking it out, especially the gaps in the aluminum components.

Otherwise, residual acid and alkali will gradually flow out in the coloring process, so that the pH of the coloring solvent exceeds the conventional category, and the color of the surface of the residual acid and alkali position is significantly different from that of the clean position, and even rust and oxidation will appear white.

Aluminum Parts Can Not be Stacked During Coloring

During the coloring process, the aluminum parts cannot be superimposed and must be placed in parallel, otherwise, the yin and yang surfaces will be generated due to the occlusion of the superimposed position.

Timely Coloring After Anodizing

Aluminum parts should be colored in time after anodizing; If the aluminum parts are exposed to the air for too long after anodizing, the film gap will become smaller, and it may be stained with dirt, resulting in inconvenient coloring.

If the coloring tank is too small, the aluminum products to be colored should be immersed in a clean water body when coloring in batches.

In order to ensure that metal products can have better performance and appearance after anodization, users first need to do two things: washing and cleaning.

types of anodizing materials

This process scrubs the metal surfaces of dust, grime, and other residues before placing them in the electrolytic bath. The purpose of this practice is to add a conductive coating containing positive and negative ions to the metal.

Anodizing Production Process Of Aluminum Parts

First of all, surface treatment and degreasing (aluminum and products, there will be dirt and defects on the surface to varying degrees. Therefore, before treatment, the surface should be cleaned as necessary to expose the pure metal matrix to facilitate smooth oxidation and coloring.

In order to obtain an artificial film that is firmly bonded to the substrate, meets the requirements of color and thickness, and has the best corrosion resistant function, wear resistance, weather resistance, and other good properties).

YIJIN Hardware metal manufacturing

The second is the process of surface cleaning in sodium hydroxide solution. It is used as a supplementary treatment after degreasing by the degreasing method, so as to further clean up the oily dirt attached to the surface, which is conducive to the formation of the anode film and obtains a higher quality film layer.

Finally, a metal or alloy product is used as an anode, and an oxide film is formed on the surface by electrolysis.

Once anodizing begins, a positive charge is transferred to the aluminum, while a negative charge is applied to the electrode plates in the electrolytic solution.

CNC aluminum products manufactured by YIJIN Hardware

Normally, the current will force positive ions to be attracted to the negatively charged ground electrode plate, and negative ions will be attracted to the aluminum metal where the positive anode is located.

Of course, there is only one purpose for this, and that is to ensure that the electrochemical reaction can open all the gaps on the surface of the aluminum metal, so as to ensure the safe leakage of + ions. This is like a uniform geometric pattern, the pores have penetrated into every substrate of the aluminum metal.

anodizing aluminum parts manufactured by yijin hardware

At this time, the combination of negatively charged ions and the aluminum surface has formed a thick barrier layer. This phenomenon is called the surface layer in the process of aluminum anodization, and the purpose is also to ensure that the parts have a lay.

Types Of Anodizing Aluminum

Anodized Type 1

This process is the simplest of the anodizing processes. The operator simply uses butyric acid to form a thin, stretchable anodized layer on the aluminum metal part.

Anodized Type II

The specific difference between anodizing type II and anodizing type I is that anodizing type II does not use butyric acid, but uses sulfuric acid to process metal parts to form a thicker protective film.

This process will not only be superior to anodizing type 1 in corrosion resistance but also improve the aesthetics of the part surface.

Anodized Type III

Anodized Type III uses sulfuric acid as the surface treatment, and the process takes a long time, so it can increase the thickness of the oxide layer of the metal parts and achieve better corrosion resistance.

Anodized Type IV/Chemical Film

Anodizing type IV is also called chemical film or Alodine.

For parts manufacturers, sulfuric acid is generally used for anodizing. Part manufacturers can choose from different anodizing aluminum methods according to the wishes of their customers.

Applications Of Anodizing Aluminum

Metal aluminum is a material that is often used in industrial production, daily life, public facilities, and aviation. Aluminum is strong, lightweight, and has good plasticity.

After anodizing, aluminum metal parts can be widely used in various fields, such as aviation, consumer goods, sports equipment, electronic products, and large-scale amusement parks.

At present, the hardness of metal parts that have undergone anodizing type III / anodizing type II operations can already meet the actual demands of different industries.

types of anodizing materials


Anodizing technology is an important surface treatment process in the production of aluminum machining parts. In recent years, with the development of modern industry, the improvement of people’s living standards, and the enhancement of environmental protection awareness, aluminum, and its alloys will play an increasingly important role in people’s daily production and life.

Therefore, the requirements for the aluminum alloy anodizing process are getting higher and higher, and the functional requirements are becoming more and more diverse.

In the production practice, it is necessary to observe, analyze and summarize many factors affecting the performance of the anodic oxide film for a long time, and master the method of improving the performance of the anodic oxide film, so as to provide a guarantee for obtaining satisfactory product quality.

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