Electroplating and Electroless Plating
Electroplating is to use the plated metal product as a cathode, and add direct current to make the cations of the metal salt solution accumulate on the surface of the workpiece to form an electroplating layer. Electroplating is essentially an electrolytic process, and the amount of material separated from the cathode is proportional to the current intensity and time. The three necessary conditions for electroplating are: power supply, aqueduct (degree liquid) and electrodes. Electroplating can cover a layer of relatively uniform and good bonding force for materials or parts, so as to change their surface characteristics and appearance, and achieve the purpose of material protection or decoration. In addition to making the product beautiful and durable, electroplating can also obtain special functions, which can improve the corrosion resistance, wear resistance, heat resistance, light reflection, electrical conductivity, lubricity, surface hardness and size of worn parts of metal products. and surface defects, such as gold plating on semiconductor devices, a very low contact resistance can be obtained; aluminum-tin alloy plating on electronic components can achieve good brazing performance; chrome plating on piston rings and shafts can achieve very high Wear resistance; copper plating to prevent local carburization, tin plating to prevent local nitriding, etc. Now, the widely used electroplating processes include copper plating, nickel plating, chrome plating, zinc plating, silver plating, gold plating, etc.
Electroless plating is also known as electroless plating without external power supply. The principle is: the metal accumulation in the aqueous solution is generally carried out as follows: M2+ + 2e → M, that is, there are two positively charged metal ions M in the solution, and when it accepts two electrons, it is converted into a metal atom M, and under appropriate conditions It is deposited on the surface of the workpiece to form a coating. Electroless plating obtains electrons directly in solution through chemical reactions, which generally include charge exchange accumulation, contact accumulation, and recovery accumulation. Now, electroless nickel plating, copper plating, silver plating, gold plating, cobalt plating, palladium plating, platinum plating, tin plating, etc. have been applied in industrial production, especially in the electronics industry.
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