What Is Electrophoretic Deposition?

Electrophoresis deposition (English name electrophoresis deposition) refers to the process of depositing colloidal particles into materials through the action of a direct current electric field in a stable suspension, which is called electrophoresis deposition. For example, a DC voltage is applied to the electrophoretic paint, and the charged paint particles move to the cathode, and react with the alkali generated on the surface of the cathode to form insoluble matter and deposit on the work surface. Therefore, electrophoretic deposition includes two processes, one is electrophoresis, and the other is deposition. ^[1]

Electrophoresis deposition (English name electrophoresis deposition) refers to the process of depositing colloidal particles into materials through the action of a direct current electric field in a stable suspension, which is called electrophoresis deposition. For example, a DC voltage is applied to the electrophoretic paint, and the charged paint particles move to the cathode, and react with the alkali generated on the surface of the cathode to form insoluble matter and deposit on the work surface. Therefore, electrophoretic deposition includes two processes, one is electrophoresis, and the other is deposition. ^[1]

Electrophoretic deposition

Electrophoresis refers to the phenomenon that solid (or liquid) particles suspended in a solution (or gas) move to an electrode opposite to the dotted symbol of the particle under the action of an electric field force. Particle deposition is believed to be due to:

(1) Particle charge neutralization: As the particles contact the electrode stabilized, the charged charges are neutralized and deposited. This mechanism is important for single-layer deposition, such as powder deposition in salt suspensions;

(2) Electrochemical coagulation of particles: the repulsion between particles decreases, and the electrolyte concentration around the particles increases, resulting in particle coagulation;

(3) Flocculation caused by particle accumulation: The electric field moves the particles toward the electrode, and the particles are deposited by the pressure of the internal and external ions.

Electrophoretic deposition

The entire electrophoretic deposition process is divided into the following four steps:

(1) Electrolysis: The initial reaction of the cathode is an electrolytic reaction, which generates hydrogen and hydroxide ions OH. This reaction causes a highly alkaline boundary layer to form on the cathode surface. When cations and hydroxides become water-insoluble substances, coating Film deposition:

(2) Electrophoresis: the process of cationic resin and H + moving to the cathode and anion moving to the anode under the action of an electric field;

(3) Electrodeposition: On the surface of the coated workpiece, the cationic resin interacts with the surface of the cathode, which neutralizes without depositing and deposits on the coated workpiece.

(4) Electroosmosis: The solid coating and the coating film on the surface of the workpiece are translucent, with most pores. Water is exuded from the cathode coating film. Under the action of the electric field, the coating film is dehydrated, and the coating The membrane is adsorbed on the surface of the workpiece to complete the entire electrophoresis process.

Classification of electrophoretic deposition

The electrophoretic deposition process is divided into the following two types due to the different composition of the suspended glue solution:

(1) Anode electrodeposition (AED): A metal workpiece is used as the anode to attract negatively charged paint particles in the glue solution. During electrodeposition, a small amount of metal ions (anodized) migrate to the surface of the coating film, and its performance on the coating film Make an impact. Anodic electrophoretic coating is mainly used for workpieces with lower requirements on corrosion resistance, and is an economical coating.

(2) Cathodic electrodeposition (CED): The metal workpiece is used as the cathode to attract the positively charged paint particles in the paint solution. Since the coated workpiece is the cathode rather than the anode, the metal ions entering the coating film are greatly reduced, thereby improving the paint. Membrane performance. The coating film is excellent and has excellent corrosion resistance.

Electrophoretic deposition application

Electrophoretic deposition is mainly used for the coating of electrophoretic paint. The electrophoretic paint film has the advantages of fullness, uniformity, flatness and smoothness. The hardness, adhesion, corrosion resistance, impact resistance, and permeability of the electrophoretic paint film are significantly better than other coatings. Craft.

The electrophoretic deposition process is also used to analyze and isolate some natural colloidal components, such as proteins, polysaccharides, nucleic acids, and so on. ^[1]