Metal Electrophoresis Finishing Services – Junying Color EPD Surface Treatment for Metal Castings

The color EPD surface treatment is a suitable for applying different colors on metal materials and products. As a one-stop die casting company, Junying is offering Color Electrophoresis Metal Finishing Services for aluminum alloy die castings, zinc alloy die casting parts, and other metal products. We can customize a wide range of electrophoresis colors based on your requirements, achieve high corrosion resistance and good protection. With nearly 20 years of experience on CNC manufacturing, mold making and castings production, not only we can produce custom metal casting supplies in complex shapes with high accuracy and affordable prices, but also provide high-quality surface treatment like electrophoresis services to improve the appearance and properties of your aluminum casting products. Fast delivery within a week, welcome to send your files or needs to us, free quotes will be send back as soon as possible.

Why Choose Our Electrophoresis Surface Treatment

Widely applied on aluminum castings, lock parts and high-grade furniture hardware
Uniform and plump coatings available in a variety of color options
Maintain metallic luster and enhance the corrosion resistance of part surface
Least influence on the product precision and dimensional stability
Can be combined with other surface treatment at Junying
Skilled in the production of metal castings and casting mold, as well as customized finishing

Details of Our Color Electrophoresis Services

Material	aluminum alloy Al-Cu4Ti, A-U5GT, AICu4Ti(3.1841), A380, etc.
Colors	red, purple, green, silver, blue, black, yellow, etc.
Process	colour electrophoresis
Application	apply different colors on die castings
Industries	automotive parts, motorcycle parts, architectural profiles, musical instruments, pens, doors and windows, furniture hardware, lighting parts, lock parts, etc.

What is Electrophoresis (EPD)?

Electrophoretic deposition (EPD) includes a range of industrial processes like electrocoating, cathodic electrodeposition, anodic electrodeposition, and electrophoretic coating, or electrophoretic painting. The electrophoretic coating is analogous to electroplating in that a voltage is applied across electrodes in a bath, the electrode coated is usually the anode. In the EPD process, the colloidal particles suspended in a liquid medium will migrate and deposit onto an electrode due to the impact of an electric field, so all colloidal particles that can form stable suspensions and that can carry a charge can be used in electrophoretic deposition, including metals, polymers, ceramics, dyes and more materials. The electrophoresis surface treatment can apply materials to any electrically conductive surface.

Advantages of Electrophoresis Metal Finishing

The electrophoresis paint film is plump, uniform, flat and smooth
Outstanding hardness, adhesion, corrosion, impact performance and permeability
Strong coating and good slippery feeling
Long-lasting bright color and high durability
Strong bonding force and penetration
Good discoloration resistance, impact resistance and anti-corrosion performance

EPD Coating Process

Electrophoretic deposition coating, a unique coating technology, involves several key steps in its process flow.

1. Workpiece Pretreatment

First of all, pretreatment before painting is essential, which involves multiple steps such as degreasing, hot water cleaning, rust removal, cold water cleaning, phosphating, hot water cleaning again and passivation.

Removal of Surface Contaminants – Cleaning removes oil stains, rust, and other impurities from the workpiece surface to ensure cleanliness.
Surface Adjustment – Chemical or physical methods are used to adjust the surface condition of the workpiece, enhancing coating adhesion.
Phosphating Treatment – A phosphating agent is used to form a phosphate film on the workpiece surface, further improving coating adhesion.

2. Base Film Coating on the Workpiece
Next is the electrophoretic coating step. In this stage, charged paint particles move directionally and deposit onto the surface of the workpiece under the influence of an electric field. The formation of an electrophoretic film on any substrate involves several complex electrochemical reactions, including the following steps:

Electrolysis – Water decomposes under electric current, producing hydrogen at the cathode and oxygen at the anode.
Electrophoresis – Positively charged colloidal resin and pigment particles move toward the cathode under the electric field.
Electrodeposition – Paint particles deposit and precipitate on the electrode.
Electroosmosis – Under the electric field, water contained in the coating film migrates from the film to the bath solution, resulting in dehydration of the film.

3. Film Curing and Washing
After forming the EPD film on the workpiece, the electrophoretic film is dried to produce a smooth and uniform coating, thus completing the entire EPD process. The final washing step aims to remove excess paint from the workpiece.

Curing – Select an appropriate curing method such as thermal curing or UV curing according to coating requirements, controlling temperature and time to ensure complete curing of the coating film.
Clean – Use cleaning agents to remove residual electrophoretic solution and impurities from the surface of the workpiece.
Inspection and Finishing – Inspect and finish the coated workpieces to ensure the coating quality meets high standards.

EPD Coating Process Types

Electrophoretic coating can be divided into cathodic and anodic electrophoresis. In cathodic electrophoresis, the coated object serves as the cathode, and the paint is cationic and positively charged. In contrast, anodic electrophoresis sets the coated object as the anode, and the paint is anionic and negatively charged.

Cathodic vs. Anodic Electrophoretic Coating Surface Treatment: Which One to Choose for Your Project?

In the anodic electrophoresis process, anodic dissolution of the workpiece occurs, resulting in slightly inferior adhesion compared to cathodic electrophoresis.
The coating film formed by cathodic electrophoresis has significantly better corrosion resistance than anodic electrophoresis. Specifically, the salt spray resistance of cathodic films can reach 720 to 1000 hours, while anodic films only reach 240 to 400 hours.
Cathodic electrophoresis has superior throwing power, easily covering internal cavities and weld seams for comprehensive coating.
Coatings used in anodic electrophoresis are alkaline, while cathodic electrophoresis coatings are weakly acidic. Thus, anodic electrophoresis equipment can use carbon steel, while cathodic electrophoresis requires stainless steel, making anodic equipment relatively less expensive.
In terms of power consumption, the coulombic efficiency of cathodic electrophoresis is 35 mg/coulomb, compared to 10–20 mg/coulomb for anodic electrophoresis, making cathodic electrophoresis more energy-efficient.

Due to these performance differences, most workpieces now tend to use cathodic electrophoretic coating. However, for workpieces with low corrosion resistance requirements, anodic electrophoresis is also a viable option.

EPD Coating Paint

Electrophoretic paints are mainly divided into two categories: epoxy electrophoretic paint and acrylic electrophoretic paint. Both types are widely used in cathodic and anodic electrophoresis systems. When selecting, users can refer to the table below to make decisions based on the pros and cons and application fields of each electrophoretic paint type.

EPD Paint Type	Advantages	Disadvantages	Applications
Anodic Epoxy	Low-temperature curing, no heavy metals, good throwing power	Poor UV resistance, limited color options	Agricultural machinery, automotive parts, steel materials, castings, engine parts, etc.
Anodic Acrylic	Good decorative effect, adjustable color, controllable gloss	Relatively weak corrosion resistance	Metal office supplies, ventilation equipment, and devices used in both interior and exterior environments with moderate conditions
Cathodic Epoxy	Corrosion resistance, chemical resistance, impact resistance, no heavy metals, low VOC content	Poor UV resistance, limited color options	Automobiles and their parts, household electrical products, etc.
Cathodic Acrylic	UV resistance, corrosion resistance, adjustable color	Relatively poorer corrosion resistance of the base coating	Eyeglass frames, leather goods, zipper pulls, door handles, locks, and other items requiring decorative effects

Please note: The information in the table above is for reference only. The actual selection should be based on the specific application scenario and requirements.

1. Anodic Epoxy Electrophoretic Paint
Anodic epoxy electrophoretic paint, with its low-temperature curing properties, is especially suitable for castings, engines, and other substrates sensitive to temperature. In the field of agricultural machinery, this paint offers many advantages. Due to the complex shapes and varying sizes of agricultural implements, traditional coating methods are often inadequate. In addition, some agricultural machinery requires low-temperature curing. Anodic epoxy electrophoretic paint not only meets these requirements but also provides excellent weather resistance, high gloss, and ensures even coating of inner cavities.

2. Anodic Acrylic Electrophoretic Paint
Anodic acrylic electrophoretic paint is economically efficient and convenient for single-layer coating, making it widely used for indoor equipment. The coating film offers a highly smooth surface, with adjustable color and gloss, and forms a hard, chemically resistant, and highly corrosion-resistant film. Therefore, it is often used for heaters, ventilation equipment, air conditioning components, and electrical gears.

3. Cathodic Epoxy Electrophoretic Paint
Cathodic epoxy electrophoretic paint is known for its outstanding anti-corrosion performance, high throwing power, and stable operation. Its unique feature is the ability to evenly coat complex workpieces, making it suitable for outdoor furniture. For users with high anti-corrosion requirements, cathodic epoxy electrophoretic paint is undoubtedly the best choice.

4. Cathodic Acrylic Electrophoretic Paint
Cathodic acrylic electrophoretic paint, as a single-coat material, can meet both anti-corrosion and high decorative requirements. Its unique color adjustability allows workpieces to be easily coated with the desired film color. Additionally, this paint demonstrates excellent chemical and alkali resistance, fulfilling diverse user needs with just one coat. Thus, cathodic acrylic electrophoretic paint is widely used for the external decoration of workpieces, providing excellent anti-corrosion and chemical resistance while giving them decorative appeal and vibrant appearances.

Electrophoretic Coating (EPD Surface Treatment) Applications

In the coating process of metal workpieces, electrophoretic coating stands out for its high degree of automation, controllability, and efficiency. Particularly in industrial production, when used as a primer, the electrophoretic coating is usually placed between the phosphating layer and the intermediate coat, serving as a crucial anti-corrosive layer. Therefore, electrophoretic paint sees diverse applications in industrial fields. Depending on the application scenario, suitable electrophoretic paint characteristics are selected to meet requirements. Below are some application examples in the industrial sector:

Agricultural Machinery: Requires electrophoretic paint with high gloss, adjustable color, strong weather resistance, and good anti-corrosion properties.
Automobile Manufacturing: Focuses on corrosion resistance, stone chip resistance, and weather resistance to ensure long-term performance.
Container Manufacturing: Requires electrophoretic paint with impermeability and chemical resistance, and must pass FDA certification for food safety.
Eyeglass Frame Production: Requires electrophoretic paint that resists artificial sweat, corrosion, and chemicals to ensure durability and comfort.

Additionally, electrophoretic paint is widely used in lighting, belt buckles, jewelry, decorative items, zipper pulls, locks, door handles, electrical switches, laboratory equipment, and more. Its high transparency, anti-corrosion, chemical resistance, and color adjustability make it indispensable in these industries.

EPD Coating (E-Coating Surface Treatment) FAQs

What Causes Uneven EPD Coating Film and How to Solve It?
Uneven coating film refers to the phenomenon where, due to various reasons during the coating process, the coating is distributed unevenly on the workpiece surface, resulting in varying thickness and color differences.
Causes: Uneven film may be caused by improper control of parameters such as the concentration, temperature, and electric field strength of the electrophoretic solution, poor workpiece surface treatment, or inappropriate coating time.
Solutions: To address uneven film, adjust parameters such as concentration, temperature, and electric field strength of the electrophoretic solution to ensure process stability and uniformity. At the same time, enhance pretreatment of the workpiece surface, such as derusting, degreasing, and dust removal, to improve surface adhesion.

What Causes Thin EPD Coating Film and How to Solve It?
Thin coating film refers to insufficient coating thickness after application, failing to achieve the expected protective and decorative effects.
Causes: Thin film may be due to low concentration of the electrophoretic solution, too short coating time, or low electrophoretic voltage.
Solutions: To address thin film, increase the concentration of the electrophoretic solution, extend the coating time, or raise the electrophoretic voltage to increase film thickness. Also, check the solution level in the electrophoretic tank to ensure sufficient solution.

What Causes Excessively Thick EPD Coating Film and How to Solve It?
Excessively thick film refers to coating thickness exceeding expectations after application, possibly resulting in surface roughness or flaking.
Causes: Thick film may be due to too high concentration of the electrophoretic solution, too long coating time, or too high electrophoretic voltage.
Solutions: To address thick film, reduce the concentration of the electrophoretic solution, shorten the coating time, or lower the voltage to decrease film thickness. Also, strengthen pretreatment of the workpiece surface to avoid excessive deposition.

What Causes Peeling EPD Coating Film and How to Solve It?
Peeling refers to poor adhesion of the coating to the workpiece surface after application, leading to easy peeling or blistering.
Causes: Peeling may result from improper surface treatment, insufficient pretreatment before coating, or poor process parameter control.
Solutions: To address peeling, enhance pretreatment such as derusting, degreasing, and dust removal to improve surface roughness and adhesion. Also, adjust parameters such as concentration, temperature, and electric field strength of the electrophoretic solution to improve coating adhesion. Regularly check and clean the tank and circulation pipes during production to ensure the quality and stability of the process.

Is EPD Coating Performed Before or After Machining?
Electrophoretic coating can be performed either before or after machining, and the timing should be decided based on specific circumstances:

Advantages and Disadvantages of Pre-Machining EPD Coating:
Performing EPD before machining better protects the material surface, increases cutting tool life during machining, and improves machining accuracy. However, it may increase material costs and processing cycle since the coating process must be completed in advance.
Advantages and Disadvantages of Post-Machining EPD Coating:
Conducting EPD after machining avoids the risk of coating damage or wear during machining and does not increase material costs or processing time. However, it may cause issues such as coating cracking or scratching, affecting product appearance and durability.