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The chief action involved in cad plating entails the application of a cadmium coating onto a conductive surface. The cadmium layer is deposited onto a plastic or metal object to offer such benefits as malleability, easier solderability, excellent lubrication, corrosion resistance, or a smooth base for applying paint or finish. This type of industrial plating is primarily used in the production of aerospace components, steel storage tanks, and fasteners. Cad plating is also an integral part of many military specifications.
The process involved in cad plating is much like any other metal plating process. Cadmium is a metallic chemical element that is soft and bluish-white in color; it shares many properties with mercury and zinc. The cadmium covering is fused to the conductive surface utilizing an electrical plating procedure called electroplating. This practice involves the deposition of cadmium in an acid solution or cyanide. The solution is then applied to the surface of the object with the aid of an electrical current, which stimulates and shifts the ions in the metal.
Though cadmium electroplating is the most common mode of application, electroless procedures are sometimes involved in cad plating creation. In electroless plating, no electricity is used. The process is accomplished by strictly chemical means. Concurrent reactions of the chemical, which has been placed in a water-based solution, create the uniform layer of cadmium on an object's surface. Electroless plating is known for crafting consistent, evenly-distributed layers and is normally employed when cadmium must be used in combination with nickel.
Despite the advantages of the finished product, there are troubling and possibly dangerous risks involved in cad plating. Cadmium possesses an exceptionally high level of toxicity, and even in unusually low amounts, it is extremely carcinogenic. The potential hazards cad plating represents to workers has raised a number of environmental and health concerns. Sweden, for example, has attempted to have cadmium outlawed because of its negative impact on health and ecology. However, certain applications demand the result that only cadmium can provide, and while there are alternatives, they do not entirely mimic the qualities of cadmium.
Gold is a healthier and more environmentally sound alternative to cadmium. The two materials have very similar properties and can be applied in this case for many of the same purposes. Gold, though, has its drawbacks. The cost is usually prohibitive, and a finished product crafted with gold plating typically does not adhere to paint as efficiently as cadmium.
Is it usually the practice to apply the cad plating to the finish sized parts. As it is soft and moves with contact from a mating part. For example, threads with cad and then a threaded object is screwed into it. The thread should not be oversize to allow for the coating - correct? Also the opposite, you would not undersize a threaded rod before applying the cad? Advise.