What is electroplating? Basic knowledge of electroplating

What is electroplating? Basic knowledge of electroplating

Ⅰ Introduction to electroplating

Electroplating is the process of using the principle of electrolysis to plate a thin layer of other metals or alloys on some metal surfaces, which is the process of using electrolysis to attach a layer of metal film to the surface of metal or other materials. During electroplating, the coated metal or other insoluble material is the anode, the workpiece to be plated is the cathode, and the cation of the coated metal is reduced to form a coating on the surface of the workpiece to be plated. In order to eliminate the interference of other cations and make the coating uniform and firm, it is necessary to use a solution containing metal cations as an electroplating solution to keep the concentration of metal cations in the coating unchanged. The purpose of electroplating is to coat a metal coating on the substrate to change the surface properties or dimensions of the substrate. Electroplating can enhance the corrosion resistance of the metal (coated metal is mostly corrosion-resistant metal), increase hardness, prevent wear, improve electrical conductivity, lubrication, heat resistance, and surface beauty.

Ⅱ Electroplating classification

Electroplating can be classified according to the composition of the coating and the way to obtain the coating, the following is our classification according to the composition of the coating.

Ⅲ Coating type and application

Chromium plating: Chromium is a metal with high hardness, which can well increase the hardness and wear resistance of the material. Chrome plating is widely used in the surface treatment of parts such as automobiles and bicycles, as well as various parts inside and outside aircraft engines.

Nickel plating: Nickel has strong corrosion resistance and can effectively prevent oxidation and corrosion on the surface of the material. Nickel plating is often used in the manufacture of circuit boards to improve the performance of the connector industry and to improve the durability of electronic components.

Galvanizing: Zinc has good corrosion resistance and can protect steel materials from corrosion and oxidation. Galvanizing occupies a large proportion in automobile electroplating, and is also widely used in machinery, transportation, electricity, construction and other industries.

Copper plating: Copper has good electrical and thermal conductivity, so it is widely used in the field of electronics, appliances and communications. On printed circuit boards, copper plating is used to protect the board and improve electrical connectivity and conductivity.

Gold plating: Gold's corrosion resistance, beauty and high weight make it an aristocrat in the electroplating industry, but the cost is higher. Gold plating is only used in situations where material requirements are extremely high, such as aviation, defense, aerospace, jewelry and other fields.

Ⅳ Basic electroplating process

1. Pre-plating treatment:

Cleaning: remove oil, dust, rust and other impurities on the surface of the plating to ensure the binding force between the coating and the substrate. Common methods include organic solvent cleaning, chemical degreasing, electrochemical degreasing, etc. For example, use organic solvents such as gasoline, alcohol, etc. to wipe the surface of the plating to remove oil; Or put the plating into an alkaline solution for electrochemical degreasing, and remove the oil by electrolytic reaction.

Pickling: The acid solution is used to remove the oxide and rust layer on the surface of the plated part, so that the surface of the substrate is exposed to the metallic luster for the subsequent plating process. Commonly used acids are hydrochloric acid, sulfuric acid, nitric acid and so on. However, adequate water washing is required after pickling to prevent acid residue.

Activation: For some substrate materials with poor surface activity, activation treatment is needed to improve the surface activity and enhance the binding force between the coating and the substrate. The methods of activation include chemical activation, electrochemical activation, etc. For example, the plating is soaked or energized in a solution containing an activator.

2. Plating operation:

Selection of electroplating solution: according to the material of the plating part, the requirements of the coating and the characteristics of the plating process, choose the appropriate electroplating solution. The composition of electroplating solution includes metal salt to provide a source of metal ions, conductive salt to improve conductivity, anode dissolution additives to prevent the anode from forming a blunt film, buffer to prevent pH value changes, complex agent, stabilizer, coating property improvement additives and wetting agents.

Set electroplating parameters: Determine the current density, voltage, temperature, time and other parameters of electroplating. Excessive current density may lead to rough and burnt coating. If the current density is too small, the coating thickness will be insufficient and the deposition speed will be slow. Too high or too low temperature will affect the performance of the plating solution and the quality of the coating.

Electroplating: Put the pre-treated plating parts into the plating tank, connect the power supply, and electroplating according to the set parameters. In the plating process, it is necessary to stir the plating solution continuously to ensure the uniform distribution of metal ions and improve the uniformity of the coating.

3. Post-plating treatment:

Cleaning: After electroplating is completed, the plating part is removed from the plating tank and cleaned with clean water several times to remove the plating solution and impurities remaining on the surface of the plating part.

Drying: Dry the plated parts after cleaning to remove moisture and prevent rust.

Inspection: The coating quality of the plated parts is inspected, including the thickness, hardness, binding force, appearance and other aspects of the coating. If quality problems are found, they need to be handled or reworked in time.

Ⅴ Electroplating process requirements

There should be good binding force between the coating and the base metal and between the coating and the coating.

The coating shall be fine crystalline, flat and uniform in thickness.

The coating shall have a specified thickness and as few pores as possible.

The coating shall have the specified indicators, such as brightness, hardness, electrical conductivity, etc.

Plating time and plating process temperature determine the thickness of the coating.

Ⅵ Role of electroplating

1. Protection performance improvement:

Enhanced corrosion resistance: The metal coating formed on the surface of metal or other matrix materials can effectively isolate external corrosive substances, such as moisture, oxygen, acid, alkali, etc., to prevent corrosion of the matrix material. For example, when the surface of steel is coated with zinc, the zinc layer will be preferentially corroded even in a humid environment, thereby protecting the steel matrix and extending the service life of the material.

Improved wear resistance: The coating can increase the surface hardness and wear resistance of the base material, so that it can withstand more friction, wear and scratching. For example, hard chromium plating on the surface of mechanical parts can significantly improve the wear resistance of parts, reduce size changes and failures caused by wear, and is suitable for a variety of friction-frequent working environments.

2. Decorative:

Beautiful appearance: It can make the surface of the product have the luster, texture and color of the metal, such as the chrome plating layer has a bright silver white luster, the gold plating layer shows a noble gold, the nickel plating layer has a soft silver gray, etc., which can improve the appearance quality and grade of the product and meet people's aesthetic needs for the appearance of the product.

Color diversity: Through different plating processes and coating combinations, rich and diverse color effects can be achieved, such as through multi-layer plating or alloy plating, you can obtain special color and appearance effects such as colored stainless steel, imitation gold plating, providing more choices for product design and decoration.

3. Functional enhancement:

Improving electrical conductivity: For some parts or electronic components that require good electrical conductivity, electroplating metals (such as gold, silver, copper, etc.) can improve their electrical conductivity, ensuring the stable transmission of current and the accurate transmission of signals. For example, electroplating on components such as connectors and printed circuit boards of electronic devices can reduce contact resistance and improve circuit reliability.

Improved weldability: Certain coatings can improve the weldability of the base material, making the welding process easier and more reliable. For example, tinning on some metal parts that need to be welded can reduce the welding temperature, improve the welding strength, and reduce the generation of welding defects.

With magnetic and other special functions: by electroplating specific magnetic materials, such as nickel-iron alloy, etc., can make the product magnetic, to meet some special application needs, such as magnetic sensors, magnetic fixtures, etc.

4. Good processability:

Good covering uniformity: During the plating process, metal ions are uniformly deposited on the substrate surface under the action of electric field, which can form a uniform and dense coating. For parts with complex shapes and uneven surfaces, good covering effect can also be obtained to ensure the quality and performance of the coating.

Strong binding force with the substrate: the coating and the substrate material form a firm combination through chemical bonding, physical adsorption and other ways, which is not easy to fall off or peel off, and can meet the requirements of the product under various conditions of use.

5. Economy:

Relatively low cost: Compared with some other surface treatment methods, such as thermal spraying, physical vapor deposition, electroplating equipment and process is relatively simple, low cost, suitable for large-scale production and application. Especially for some small parts and mass production products, electroplating can reduce production costs under the premise of ensuring quality.

Repairability: If the coating on the surface of the product appears wear, scratches and other defects, it can be repaired by re-plating to restore the performance and appearance of the product, extend the service life of the product and reduce the waste of resources.

Ⅶ Application of electroplating

Automobile industry: bumper, door handle, wheel hub, radiator, piston, piston ring, bearing bush, inlet and exhaust valve, shock absorber connecting rod, etc.

Electronics industry: Printed circuit board, electronic connectors, mobile phone shell, semiconductor manufacturing, etc.

Aerospace field: aircraft wings, fuselage structure, engine blades and other key components, spacecraft solar panel frame, antenna, gyroscope and so on.

Medical instruments: surgical instruments such as scalpels, tweezers, scissors, artificial joints, dental implants, etc.

Construction industry: door and window handles, hinges, locks, etc., metal curtain wall, metal railing, metal sculpture, etc.

Light industry: faucets, showers, tableware, kitchenware, pens, metal toys, model cars, robots, etc.

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