What is plating?
Plating is surface processing that covers the surface of a workpiece that becomes the base material with a thin metal film. There are roughly three purposes for plating.
• Improved decorative properties
It is plating to improve the aesthetic appearance, for example, to create a shiny surface, a high-end color, etc. The representative one is gold plating.
• Improved corrosion resistance
Some materials such as iron commonly used in industrial products are prone to rust. Therefore, the surface is covered with corrosion-resistant metal, which is plating to avoid rust. Galvanizing, etc. are its representatives.
• Improved functionality
In addition to decoration and corrosion resistance, plating can add various functions. For example, in plating to optimize the suitability of solder called solder wettability, nickel plating is performed, or an alloy of copper and tin is used for plating. In addition, there are also plating to improve sliding properties or improve electrical conductivity.
Plating and types
In mechanical processing, electroplating is the most common method of plating and is used to make materials decorative, rust-proof, wear-resistant, and conductive.
Electroplating is the most common method of plating and is used to make materials decorative, rust-proof, wear-resistant, and conductive. Put the metal to be plated and the coating metal into a solution containing metal ions, connect the metal to be plated to the cathode, connect the coating metal to the anode, and pass on a direct current. As a result, a reduction reaction occurs in the solution, and the coating metal is precipitated on the metal surface of the anode.
The amount of metal deposited changes with current density, so the thickness of the plating becomes uneven depending on the shape of the part. Specifically, the plating is thicker in protruding parts and thinner in recessed parts. The plating thickness of electroplating will vary depending on the current and time passed, so it is necessary to find the plating thickness that meets the purpose for each plated part.
Electroplating mainly includes the following categories.
gold plated
Gold is a metal with beautiful luster, but is expensive. Therefore, only the surface of the product is covered with gold, and gold plating is performed to enhance the decorative properties. Not only is gold beautiful in appearance, but it is also chemically stable and therefore has excellent corrosion resistance. It can also be used for anti-rust purposes and to improve electrical conductivity.
silver
Silver is also a metal with excellent decorative properties like gold. However, since it is easily oxidized, it is necessary to perform treatment to prevent discoloration after silver plating. Due to its high conductivity, it is used for surface treatment of connector parts of precision equipment, etc.
galvanized
This is the most commonly used processing method for anti-rust plating. When galvanizing carbon steel parts, it prevents corrosion of the carbon steel due to its self-sacrificial effect on the carbon steel. After galvanizing, perform gloss galvanizing and trivalent chromate gloss treatment to protect the zinc coating.
chrome
Chrome plating is performed to give decorative plating a glossy finish. In addition, it has strong wear resistance and excellent corrosion resistance, so it is also used in mechanical parts in the industrial field.
Electroless plating and types
In machining, electroless plating is a plating method that does not use electricity.
Electroless plating is a plating method that does not use electricity. The product to be plated is immersed in a solution containing metal ions that form the coating, so that the metal ions are reduced to form a coating. Since electricity is not required, non-conductors such as resin can be plated. At this time, since the metal film formed on the surface is conductive, electroless plating is sometimes performed on non-conductive products to make them conductive as a pretreatment for electroplating.
Nickel plating is a common plating in electroless plating.
electroless nickel plating
This is a plating method also known as electroless nickel plating. The thickness of the coating is more stable than electrolytic nickel plating, but the temperature of the plating solution is higher, so you need to pay attention. Electroless nickel plating has excellent wear resistance and rust resistance.
Other plating
In addition to electroplating and electroless plating, there are also chemical conversion treatments (black oxide film), anodizing treatments (aluminum oxide), hot-dip galvanizing, etc.
Chemical formation treatment (black oxide film)
Use chemical conversion treatment when, for example, you want to obtain a black surface. Also known as blackening treatment, an iron oxide film is formed. The thickness of the coating is thin and stable, and it can also be implemented on parts with strict dimensional tolerances.
Anodizing (aluminum oxide)
The method of forcibly oxidizing the surface of an aluminum material to obtain a coating is called anodizing. High hardness and excellent corrosion resistance.
hot dip galvanized
Hot dip galvanizing is a method of immersing parts in a heated and molten solution to form a coating on the surface. Used for wires, structures, etc. Because it is immersed in molten zinc, the effect of heat is greater.
