Introduction
The design of home appliances has evolved significantly over the past decade. In the past, “functionality was the top priority,” and appearance was often secondary. However, today, appliances placed in kitchens and living rooms are considered part of the interior design, and factors like aesthetics and a high-end feel directly influence purchasing decisions.
In this trend, aluminum is gaining attention. Compared to iron and stainless steel, aluminum is lightweight with a specific gravity of 2.7 (about 1/3 that of iron), making it easy to handle. Furthermore, it offers a wide range of processing options such as cutting, pressing, and die-casting, and can be used for thin-walled or complex shapes. While possessing the high-quality texture unique to metal, it is also highly recyclable, and its adoption is increasing from an environmental perspective.
On the other hand, aluminum’s surface is soft and susceptible to scratches and wear. In its raw state, its gloss and texture can easily degrade, making it difficult to maintain the beautiful appearance required for home appliances over the long term. This is where “surface treatment” becomes necessary. By applying treatments like anodizing, plating, or painting, it is possible to maintain appearance, improve durability, and add extra functionality.
In other words, aluminum surface treatment in home appliances is not merely a means of rust prevention or strength improvement, but a value-creating element that supports product design and the user experience.
Basic Knowledge of Aluminum Surface Treatment
Characteristics of Aluminum and Its Use in Home Appliances
With a specific gravity of 2.7, aluminum is lighter than iron and copper, which can significantly reduce the burden during transportation and assembly processes. Therefore, it is widely used in everything from small, portable products to large appliances that require both strength and lightness.
Furthermore, its excellent thermal and electrical conductivity makes it suitable for parts of air purifiers and microwave ovens that require heat dissipation, as well as for switch panels that utilize its conductive properties. Additionally, since it can be processed using various methods like pressing, cutting, and die-casting, it is a suitable material for housings and decorative parts with complex designs and features.
However, aluminum has a weakness: its surface is soft and easily scratched. Since its appearance is prone to deterioration due to wear and corrosion, appropriate surface treatment is essential to maintain the reliability and high-end feel of a home appliance.
Types of Surface Treatment and Comparison of Their Characteristics
Various methods of surface treatment for aluminum are used to achieve both “beauty” and “functionality.” The main types are as follows:
- Anodizing (White/Hard)This treatment forms an oxide film on the aluminum surface. White anodizing provides a clean look and is often used for control panels. Hard anodizing creates a high-hardness film of HV400 or more, making it suitable for parts subject to wear, such as hinges and sliding components.
- Chrome/Nickel PlatingThis gives a metallic luster and creates a high-end look. Chrome is suitable for mirror finishes, while nickel enhances corrosion resistance and smoothness. It is often used for decorative parts and around control buttons.
- Powder Coating/Liquid CoatingThese allow for a wide range of color expressions. Powder coating provides a thick, durable film, while liquid coating offers a smooth texture, making it suitable for parts where design is a priority.
- Chemical Conversion Coating/Electroless Nickel PlatingChemical conversion coating is used as a base for painting or adhesion to improve bonding. Electroless nickel plating forms a uniform film, providing corrosion resistance while maintaining the dimensional accuracy of precision parts.
As seen, the choice of aluminum surface treatment depends on the application, required functionality, and cost. For home appliances, treatments that satisfy both appearance and durability are particularly important.
Case Study 1: Rice Cooker Control Panel (White Anodizing)
A rice cooker is more than just a cooking appliance; it has become an object that enhances the kitchen space. The control panel, in particular, is an area that is touched daily, requiring a sense of luxury, cleanliness, and durability.
In this case, pure aluminum A1100 material was used, and surface homogenization by etching + white anodizing was performed. White anodizing not only forms an oxide film to enhance corrosion and wear resistance but also makes fingerprints and sebum stains less noticeable, maintaining a clean appearance. Furthermore, the matte finish improves the visibility of the LED display.
In addition, this treatment offers an excellent balance between cost and aesthetic quality, making it suitable for mass-produced, mid-priced rice cookers. As a result, it became a valuable option for both manufacturers and users, satisfying the needs for a “high-end feel,” “stain resistance,” and “cost-effectiveness” simultaneously.
Case Study 2: Air Purifier Housing Cover (Black Anodizing + Dyeing)
Since air purifiers are placed in living rooms and bedrooms, harmony with the interior is crucial. For the housing cover, black anodizing (dyeing) was chosen to give it a sense of luxury and calmness.
However, the commonly used ADC12 (aluminum die-cast material) has a high silicon content, which tends to cause non-uniform formation of the anodized film, leading to issues like uneven color and inconsistent shades. To address this, a special pretreatment was introduced to homogenize the surface, and by optimizing the processing conditions, a deep black color was consistently achieved.
Furthermore, by proposing multiple color variations such as gray and dark brown in addition to black, the appliance manufacturer was able to differentiate its product lines. This is a prime example of achieving both design aesthetics and mass productivity while overcoming material constraints.
Case Study 3: Microwave Oven Hinge Part (Hard Anodizing)
Microwave oven doors are opened and closed frequently, so the hinge parts require wear resistance and strength. The solution adopted here was hard anodizing.
Hard anodizing is performed under lower temperature and higher voltage conditions than regular anodizing, forming a high-hardness film of HV400 or more. As a result, slidability improved, leading to smoother opening and closing, which contributed to reduced operating noise and an improved user experience.
Moreover, this film has excellent corrosion resistance, allowing it to maintain stable performance over the long term in the high-temperature and high-humidity kitchen environment. This also resulted in benefits such as a reduced frequency of parts replacement, extended product lifespan, and lower after-sales service costs. It is a successful case of achieving both improved reliability and cost efficiency for a home appliance.
Design and Manufacturing Considerations for Surface Treatment
While aluminum surface treatment enhances design and durability, neglecting considerations at the design stage can lead to problems.
- Consideration for Dimensional ChangesAnodized films grow approximately 1/3 outward and 2/3 inward. For example, forming a 10µm film increases the outer diameter by about 3µm. With plating, the film thickness is added directly, so careful tolerance design is necessary for sliding and fitting parts.
- Surface Properties for Adhesion and AssemblyHard anodized surfaces are smooth, making it difficult for adhesives to bond, whereas chemical conversion coatings are effective as a base to enhance adhesion. For bolted joints, a design margin is needed to prevent film cracking or peeling.
- Pre-planning at the Mold Design StageFor die-cast products, the condition of the cast surface and molten metal flow affects the finish of the subsequent treatment. To obtain a uniform surface, it is essential to incorporate considerations for surface treatment from the mold design and release agent selection stages.
It is important to view surface treatment not as a “post-process,” but as an element that runs through design, manufacturing, treatment, and assembly.
Possibility of Procuring Surface Treatment in Vietnam
Vietnam is attracting attention as an overseas procurement destination. Against the backdrop of advantages in labor costs and supply chain diversification, its use in the field of aluminum surface treatment is expanding.
Daiwa Vietnam’s Capabilities
Daiwa Light Alloy Industry Vietnam can handle everything from pretreatment to surface treatment, focusing on aluminum castings and die-cast materials. They can achieve both design and durability even with materials that are difficult to anodize, such as ADC12, using their proprietary technology.
VA/VE Proposals and Short Lead Time Response
The company goes beyond simple contract processing, achieving cost reductions and performance improvements through VA/VE (Value Analysis/Value Engineering) proposals. For one home appliance manufacturer’s housing, they optimized treatment conditions, reducing costs by about 15% while maintaining aesthetic quality. In addition, their integrated production system at the Vietnam base enables short lead time responses.
Japanese Quality × Cost Advantage
A major strength is their ability to offer the cost advantages unique to Vietnam while maintaining quality standards under the technical guidance of their Japanese headquarters. In other words, it is a realistic option to lower procurement costs without sacrificing quality.
Conclusion
Aluminum surface treatment in home appliances is a core technology for achieving both design and functionality. By selecting the appropriate treatment according to material properties and applications, it is possible to realize both user comfort and manufacturer cost efficiency.
In the future, the use of environmentally friendly treatment technologies (such as hexavalent chromium alternatives and low-VOC paints) and composite treatments (such as anodizing + painting, plating + PVD) is expected to expand.
Overall, aluminum surface treatment is not just about “compensating for the weaknesses of the material” but continues to grow in importance in the home appliance industry as a means of creating product value.
Sources:
- Osaka Mekki Anodize Navi (https://osaka-mekki.com/contact/)
- Daiwa Light Alloy Vietnam (https://daiwakk-vn.com/)
- Silvec Technical Materials (https://www.mekkikakou.com/aluminum-increase-value/)