Hard Chrome Plating - The solution to industrial wear and tear
Hard chrome plating is one of the forms of chrome plating used to coat non-metallic articles with layers of chrome. Chrome plating is a finishing treatment.It utilizes the electrolytic deposition of chromium. The usual form of chrome plating is the thin chrome layer which is typically a 10 micrometer layer over an underlying nickel plate. It is a thin layer and is used for decorative purposes. It gives a mirror-like finish to items such as metal furniture frames and automotive trim. Thicker layers up to a thickness of 1000 micrometers, are called hard chrome and are used in industrial equipment to reduce friction. This turn reduces the wear restores the dimensions of equipment that has experienced wear.
Industrial and decorative are the two types of chromium plating. Industrial chromium plating is also called Hard Chrome or Engineered Chrome i.e. hard chrome plating.There are two types of Industrial chromium plating solutions,Hexavalent chromium baths whose main ingredient is chromic anhydride and Trivalent chromium baths whose main ingredient is chromium sulfate or chromium chloride. Trivalent chromium baths are not very common, as they have restrictions imposed on them concerning color, brittleness, and plating thickness.
Typical bath composition of a hexavalent bath is chromic acid, sulphuric acid,anodes of lead with tin or antimony, solution of sodium hydroxide. The operating temperature of this process is 45 to 60 degrees centigrade. Plating current is also passed. These materials are very toxic. They are corrosive and not eco-friendly. The government has imposed restrictions on their use and storage. Proper care must be taken while handling these materials.
Hard chromium layers, that is layers over ten micrometers thickness can be used in various applications. Thus they are subject to different types of quality requirements. For example,hard chromium layers on piston rods of hydraulic cylinders are tested for resistance to corrosion in salt spray cabinets. These are destructive tests and that is why only representative samples can be tested for resistance. The salt spray solutions and the conditions in the cabinet are normed . So also the evaluation of the result after the test. The duration of the test depends on the aggression of the test and the general expectation the industry has developed for this type of material. Normally there is a requirement that the deposit be uniform in thickness on all surfaces. The finishing should be smooth and homogeneous. There must be no frosty areas, pin holes, pits, nodules, and other defects.
There are a number of chrome plating methods. In one method, a solid surface is covered with a metal sheet and plated by heating. Other plating techniques include vapor deposition under vacuum, sputtering, and methods using vacuum conditions or gas. Metallizing is the process of coating metal on non-metallic objects.Chrome plating has become a key technology for the development of new machines especially more so hard chrome plating.