Cadmium plating is a popular method of coating items with a thin layer of metallic cadmium, providing excellent corrosion resistance, low friction, and high conductivity. It is achieved through electroplating, mechanical plating, or vacuum deposition. However, its use has come under scrutiny due to environmental concerns.
Cadmium is a material deposition process that coats items with a thin protective layer of metallic cadmium. The coatings are applied in a number of ways, including electroplating which involves immersing the receiving objects in vats of cadmium salt solution through which an electric current is passed. Other cadmium processes include mechanical and vacuum methods for smaller items and to impart highly uniform coatings. Cadmium is a popular plating material because it gives recipient items excellent corrosion resistance, low coefficients of friction, and high electrical conductivity. However, the use of cadmium as a plating material has come under close scrutiny due to environmental issues.
Metal plating is a commonly used method of coating one material with thin layers of another to protect or enhance the recipient’s features or appearance. These processes are used to deposit metallic coatings onto other metals, and some processes can also be used to coat paper products and plastic films. Cadmium plating is a popular and widely applied form of metal plating and is used to coat a wide variety of items ranging from tiny springs and clips to substantial machine parts. Cadmium gives plated items exceptional resistance to conventional and galvanic corrosion and also offers a degree of sacrificial protection. It has excellent coefficient of friction and electrical conductivity values, is strong, easily weldable, and has good torque characteristics.
Cadmium plating is achieved in several ways, the most common of which is the electroplating method. This process involves suspending the recipient items in a bath filled with an alkali cyanide-based cadmium salt solution. A cadmium anode is placed in the bath and a current is passed from it through the solution and to the receiving elements which act as a cathode or negative point. The cadmium is attracted and deposited on the receiving elements by the solution and replaced by material by the anode which is forced into solution. The cadmium electrodeposition method is characterized by good film thickness control, excellent gloss finish and good covering characteristics.
Other cadmium free methods include mechanical plating which involves rolling the recipient items in a drum with cadmium powder, glass beads and specially formulated chemicals. While effective, this process is only suitable for objects that can be shaken in this way. One of the more specialized cadmium methods is the vacuum deposition method in which the cadmium is heated in a vacuum until it evaporates. A receiving substrate is exposed to vapor where cadmium atoms adhere to its surface imparting a very thin, accurate, high quality cadmium coating. Despite its many benefits and continued use, however, cadmium as a plating material has recently attracted significant negative attention due to environmental concerns related to its high toxicity.
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