• June 21, 2024
  • Shatou, Changan, Dongguan, CN
Surface Treatment

Our Popular Metal Surface Treatment Process

Metal surface treatment is a technique that creates a layer on a material’s surface, modifying its mechanical, physical, and chemical characteristics. The layer provides the material with excellent adhesion and resistance to corrosion. This technology was one of the first adopted by humans and is aimed at fulfilling the requirements of various product functions, including wear resistance, corrosion resistance, and decoration.

Summary of metal surface treatment methods

1. Anodizing

The process of anodic oxidation of aluminum is based mainly on electrochemical principles. It creates a layer of aluminum oxide film (Al2O3) on the surface of aluminum and its alloys. This layer of oxide film provides distinct characteristics, such as protection, decoration, insulation, and resistance against wear and tear.

Process Flow:

Monochrome, gradient color:

Polishing/sandblasting/drawing→degreasing→anodizing→neutralization→dyeing→sealing→drying

Two-color:

①Polishing/sandblasting/drawing→degreasing→masking→anodizing 1→anodizing 2→sealing→drying

②Polishing/sandblasting/drawing→oil removal→anodizing 1→radium engraving→anodizing 2→sealing→drying

Technical Features:

1. Increase strength.

2. Realize any color except white.

3. Achieve a sealing process that is free of nickel and compliant with the regulations established by Europe, the United States, and other nations regarding nickel content.

Disadvantages and Disadvantages of Anodizing

Advantage:

1. Protect the metal surface: It can form a dense oxide film, which can effectively prevent the corrosion and oxidation of the metal surface.

2. Improve hardness and wear resistance: Through anodic oxidation treatment, the hardness of the metal surface can be improved, which improves the wear resistance and corrosion resistance of the material.

3. Improve the appearance: It can make the metal surface show rich color and luster, which improves the aesthetics of the product.

4. Enhance adhesion: It can increase the roughness of the metal surface and improve the adhesion of other coatings.

Shortcoming:

1. Not suitable for all metals: it is mainly suitable for active metals such as aluminum and magnesium, and it is less effective for other metals such as iron and steel.

2. Difficult to control the thickness: Its film thickness is difficult to control precisely, and there may be uneven thickness.

Technical difficulties and key points for improvement:

The success rate of a process called anodic oxidation is directly linked to the price of the end product. The secret to enhancing this process lies in adjusting the amount of oxidizing agent, setting the right temperature and current density. To fully achieve this, makers of structural components must continually experiment and strive for new innovative ways to push the boundaries of their production process.

2. Electrophoresis ( ED-Electrophoresis deposition )

When used in stainless steel, aluminum alloys, etc., these materials can create various colors in the product while retaining its metallic luster. Additionally, these materials enhance the surface performance of the product, providing excellent anti-corrosion properties.

Process Flow:

Pretreatment→electrophoresis→drying

Features of electrophoresis technology

ED-electrophoretic deposition technology has the technical characteristics of good coating uniformity, high control precision, good corrosion resistance, material and energy saving, and environmental friendliness.

Advantages and disadvantages of electrophoresis

Advantage:

1. Rich colors.

2. No metal texture, suitable for sandblasting, polishing, wire drawing, etc.

3. Processing in a liquid environment can realize the surface treatment of complex structures.

4. The technology is mature and can be produced in batches.

Shortcoming:

The ability to hide defects is average, and the electrophoresis of die castings has higher requirements for pretreatment.

3. Micro arc oxidation (MAO)

The process of applying a high voltage in an electrolyte solution (usually a weakly alkaline solution) to form a ceramic surface film layer is the result of the synergistic effect of physical discharge and electrochemical oxidation.

Process flow:

Pretreatment→hot water washing→MAO→drying

Features of Micro-arc Oxidation Technology

Micro-arc oxidation technology is a new surface treatment technology that forms a dense oxide film on the metal surface. It is characterized by simple process, low cost, fast processing speed, clean and environmentally friendly, and the generated oxide film has good corrosion resistance, wear resistance and decorative properties, which can effectively improve the service life and surface quality of metal materials.

Advantages and disadvantages of micro-arc oxidation

Advantage:

1. Ceramic texture, dull appearance, no high-gloss products, delicate hand feeling, anti-fingerprint.

2. Wide range of substrates: Al, Ti, Zn, Zr, Mg, Nb and their alloys.

3. The pre-treatment process is simple, and the product has excellent corrosion resistance, weather resistance and good heat dissipation performance.

Shortcoming:

At present, the color options are limited with only black and grey being relatively mature, while bright colors are currently difficult to achieve. The cost of achieving these colors is primarily impacted by high power consumption, which is one of the biggest expenses involved in surface treatment.

4. PVD vacuum plating

Physical vapor deposition (Physical vapor deposition, PVD):

It is an industrial manufacturing process that mainly uses physical processes to deposit thin films.

Process Flow:

Cleaning before PVD → vacuuming in the furnace → target washing and ion cleaning → coating → coating is completed, cooling out of the furnace → post-processing (polishing, AFP)

Technical Features:

PVD (Physical Vapor Deposition, Physical Vapor Deposition) can coat metal surfaces with high-hardness and high-wear-resistance cermet decorative coatings.

Disadvantages and disadvantages of PVD vacuum plating

Advantage:

1. High film quality: It can form a uniform, dense film with high hardness and wear resistance.

2. Strong film adhesion: it can form better adhesion on the substrate and is not easy to peel off.

3. Controllable film thickness: By adjusting process parameters, the thickness of the film can be controlled to meet different needs.

4. Environmental protection and energy saving: Compared with the traditional chemical gold plating process, PVD plating has less impact on the environment and lower energy consumption.

Shortcoming:

1. High equipment cost: equipment is expensive and requires high investment costs.

2. Relatively long production cycle: The PVD electroplating process takes a long time and the production cycle is relatively long, which is not suitable for mass production.

3. Film thickness limitation: The film thickness of PVD electroplating is usually thin, generally between 0.1 micron and several microns, which is not suitable for applications that require thicker coatings.

4. Limited selection of materials: Since PVD electroplating is carried out by evaporation and deposition, only materials with higher evaporation temperatures can be selected for electroplating, which has certain limitations.

5. Electroplating

This technology uses electrolysis to apply a metal film layer on the surface of metal in order to prevent corrosion and enhance wear resistance, conductivity, and reflectivity. Moreover, it is utilized to improve the appearance of the metal.

Process Flow:

Pretreatment → cyanide-free alkali copper → cyanide-free cupronickel tin → chrome plating

Electroplating technical characteristics

Electroplating technology has the characteristics of high efficiency, energy saving and environmental protection, and can greatly improve the hardness, corrosion resistance and decorative effect of the material surface. At the same time, electroplating can cover various complex shapes and small-sized objects, ensuring stable product quality and certain ductility and plasticity.

Disadvantages and Disadvantages of Electroplating

Advantage:

1. The coating has high gloss and high-quality metal appearance.

2. The base material is SUS, Al, Zn, Mg, etc.; the cost is lower than PVD.

Shortcoming:

Environmental protection is inadequate and the risk of environmental pollution is relatively high.

6. Powder coating

The powder coating is sprayed onto the surface of the workpiece by powder spraying equipment, like the electrostatic plastic spraying machine. Under the effect of static electricity, the powder is evenly adsorbed on the surface of the workpiece, forming a powdery coating. The coating is then flattened and cured to create the final coating with various effects, depending on the type of powder coatings used.

Process flow:

Loading→electrostatic dust removal→spraying→low temperature leveling→baking

Technical characteristics of powder coating

Powder coating has technical characteristics such as high solid content, no solvent volatilization, strong environmental protection, high coating quality, strong corrosion resistance, and high construction efficiency.

Advantages and disadvantages of powder coating

Advantage:

1. Rich colors, high gloss and matte optional.

2. Low cost, suitable for architectural furniture products and shells of heat sinks, etc.

3. High utilization rate, 100% utilization, environmental protection.

4. Strong ability to cover defects.

5. Can imitate wood grain effect.

7. Metal wire drawing

It is a surface treatment method that forms lines on the surface of the workpiece by grinding the product to achieve a decorative effect. Depending on the different textures from wire drawing, it can be divided into four types: straight wire drawing, chaotic wire drawing, corrugated, and swirling.

Technical Features:

The brushed treatment can give the metal surface a metallic luster that is not mirror-like. Additionally, the brushed treatment can eliminate slight flaws on the metal surface.

Advantages and disadvantages of metal wire drawing

Advantage:

1. High strength: Metal wire drawing is usually made of high-strength metal, which has high resistance to compression, tension and wear.

2. Good corrosion resistance: Metal wire drawing usually has good corrosion resistance, can be used in harsh environments, and is not easy to be corroded.

3. Good conductivity: Metal wire has good conductivity and can be used to transmit power and signals.

4. Good thermal conductivity: Metal wire drawing has excellent thermal conductivity, which can effectively conduct heat.

5. Good processability: Metal wire drawing is easy to process and plastically deform, and can be made into products of various shapes and sizes.

Shortcoming:

1. Easy to rust: Some metal wires are easily oxidized and corroded, and anti-corrosion measures need to be taken.

2. Heavy weight: Compared with other materials, brushed metal is usually heavy and not suitable for applications that require lightweight.

3. High cost: metal wire drawing usually needs to go through multiple processes, which is more complicated, so the cost is higher.

4. Limited plasticity: the plasticity of metal drawing depends on the properties of the metal, and some metal drawing may have limited plasticity.

5. Decreased electrical conductivity: Some metal wires may experience decreased electrical conductivity during use, requiring maintenance and maintenance.

8. Sandblasting

It is a process that uses compressed air as a power source to form a high-speed jet beam. This stream is used to spray the material onto the surface of the workpiece to be treated at high speed. This technique is effective in changing the appearance or shape of the workpiece’s surface. The process yields a certain degree of cleanliness and alters the roughness of the surface.

Technical Features:

1. Realize different reflective or matte.

2. It can clean the small burrs on the surface of the workpiece and make it smoother, eliminating the harm caused by burrs and improving the quality of the workpiece.

3. Clear the residual dirt left during pre-treatment, improve the smoothness of the workpiece, and make it reveal a uniform and consistent metal color. 

Advantages and disadvantages of sandblasting

Advantage:

1. Thorough decontamination: Sand blasting can completely remove the dirt, oxide layer and coating on the surface of the object, making the surface completely clean.

2. Improve adhesion: The surface of the object after sandblasting will produce roughness, which can increase the adhesion between the object and the coating and improve the durability of the coating.

3. Enhanced surface quality: Sand blasting can provide a uniform and consistent surface quality, eliminating unevenness and defects on the surface of objects.

Shortcoming:

1. Dust production: A large amount of dust will be generated during the sandblasting process, which poses potential risks to the health of workers and requires appropriate protective measures.

2. Damage to the surface of the object: If not done properly, sandblasting can damage the surface of the object, causing damage such as scratches or dents.

3. Restricted use: Abrasive blasting is generally suitable for strong and durable materials and may not be suitable for soft or fragile materials.

9. Polishing

The workpiece surface can be modified by using flexible polishing tools, abrasive particles or other polishing media.

For different polishing processes, such as rough polishing (a basic polishing process), medium polishing (a finishing process), and fine polishing (a glazing process), choosing the appropriate polishing wheel can achieve the best polishing effect and improve polishing efficiency at the same time.

Technical Features:

Improve the dimensional and geometric shape accuracy of the workpiece to achieve a smooth surface or mirror-like shine. Simultaneously, eliminate any glare.

Advantages and disadvantages of polishing

Advantage:

1. Improve the appearance: Polishing can make the surface of the object smoother and brighter, making it more beautiful in appearance.

2. Enhance corrosion resistance: Polishing can remove oxides, rust, etc. on the surface of objects, thereby reducing the degree of corrosion of objects and prolonging their service life.

3. Improve optical performance: Polishing can remove scratches, bubbles and other defects on the surface of objects, and improve the transparency and clarity of optical equipment.

4. Improve functional performance: Polishing can improve the friction coefficient of the object surface, make it have better sliding performance, reduce energy consumption and wear.

5. Easy to clean: The polished surface is smoother, not easy to accumulate dust, and easy to clean.

Shortcoming:

1. It takes time: Polishing usually takes a long time to complete, which has a certain impact on production efficiency.

2. Damage cannot be completely repaired: Although polishing can repair some surface damage, it may not be able to completely repair damage such as deep scratches and scratches.

3. Potential damage to the surface layer: Polishing may damage the layer of material on the surface of the object, especially for high-end surface treatments such as thin film coatings, which require special care.

10. Etching

Usually, it refers to etching, also known as photochemical etching. It involves removing the protective film from the area to be etched after plate-making and development. During etching, the area is then exposed to a chemical solution that achieves the effect of dissolution and corrosion, forming a concave-convex or hollow molding.

Process Flow:

Exposure method:

The project prepares the material size according to the graphics-material preparation-material cleaning-drying→film or coating→drying→exposure→development→drying-etching→stripping→OK

Screen printing method:

Cutting → cleaning plate (stainless steel and other metal materials) → screen printing → etching → stripping → OK

Technical characteristics of etching

Etching is a technology that uses chemical solutions, lasers or other tools to etch the surface of materials. It has the characteristics of high precision, microfabrication, and no contact and heat source. It enables depth control on metals, plastics, ceramics, and more for a variety of applications including micro-parts, printed circuit boards, and textures.

Advantages and disadvantages of etching

Advantage:

1. Can carry out micro-processing of metal surface.

2. Give the metal surface a special effect.

Shortcoming:

Most corrosive liquids used for etching, such as acids and alkalis, are harmful to the environment.

Summarize

In general, the metal surface treatment process has a wide range of applications and important significance in modern manufacturing. Through different treatment processes, metal products can obtain better corrosion resistance, wear resistance and appearance texture, so as to meet the needs of the market and consumers.

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