What is Cadmium Electroplating
By electrolysis. Method of depositing a layer of cadmium on the surface of steel parts. Used to prevent seawater or salt spray corrosion, improve assembly tightness and harmony, and increase beauty. Widely used in shipbuilding parts, marine instruments, instruments and fasteners and other manufacturing industries, is divided into acid cadmium plating (cadmium sulfate or cadmium fluoroborate as the main component of the electrolyte) and cadmium cyanide cyanide Nickel, sodium hydroxide and sodium cyanide as the main components of the electrolyte). Cyanide plating cadmium electrolyte preparation is simple, high distribution capacity, plating complex parts, cadmium plating crystal fine and strong binding, the application is more, is the application of non-cyanide electrolyte, with a neutral ammonium salt and ammonia Carboxy complex agent - ammonium salt and so on. After plating, passivation in chromic acid solution, rinsing and drying.
Cadmium Electroplating characteristic
Cadmium in the marine atmosphere or sea water contact parts and hot water above 70 ℃, cadmium coating is relatively stable, corrosion resistance, it is commonly used in marine plating cadmium plating.
Cadmium is a silvery white plasticity metal. Cadmium metal is easy to forge and roll. The relative atomic mass of cadmium is 112.41, the density is 8.65g / cm3, the melting point is 320.9 ℃ and the boiling point is 767 ℃. Cadmium is present as a divalent metal in compounds. Its hardness is 200HV. The chemical properties of cadmium and zinc are very similar, but not soluble in lye, soluble in nitric acid and ammonium nitrate, dissolved in dilute sulfuric acid and dilute hydrochloric acid is very slow. In room temperature and dry air, almost no chemical changes, but in humid air, cadmium is easy oxidation, the formation of the oxide film can protect the metal cadmium will not continue to be corroded.
Cadmium vapor and soluble cadmium salts are toxic, we must strictly prevent the pollution of cadmium. The standard potential of cadmium is -0.4V. In general industrial atmosphere, cadmium plating is a cathode coating on steel parts, but cadmium plating is anodic coating on steel parts in maritime climate, seawater or high temperature environment. When the operating temperature exceeds 232 ℃ above, cadmium coating easily lead to brittle parts.
Cadmium plating is commonly used in aerospace, marine, radio and electronic product protection.
The domestic application of more types of cadmium plating solution are: ammonia carboxylate-cadmium plating, acid sulfate cadmium plating and cyanide cadmium plating. In addition, there are pyrophosphate cadmium, alkaline triethanolamine cadmium plating and HEDP cadmium plating.
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