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Chrome Plating process for plastics PDF Print E-mail
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Tuesday, 26 May 2009 05:29
Chrome plating of plastic is significantly more difficult than performing the same operation on a metal, but it will provide excellent results when the right process is utilised. Due to the chrome plating process requiring the part to be electrically conductive, a series of steps are required before the chrome can be deposited onto the surface of the product.

    The first step to be carried out is to etch the surface with a chemical so that the subsequent layers of nickel and chromium will adhere. A large proportion of plastic parts that will be chrome plated will be moulded from ABS as this gives a very good surface finish to plate onto. ABS is also used because the butadiene molecules on the surface of the material can be chemically removed. This removal of butadiene molecules leave microscopic undercuts in the surface of the ABS and this acts as a very good key onto which the first layer can be attached .

    The next process that will be carried out is to attach a layer of nickel (with a catalyst) onto the surface of the part. This layer of nickel will be what becomes electrically conductive and allows the chrome to be electroplated to it. This layer is applied by means of dipping the product. The key that was put into the surface of the part will ensure the nickel remains attached when the part is removed from the bath.

    Once the layer of nickel has dried the part can be plated by electroplating. This involves applying a negative charge to the part being plated and dipping it into a solution of the metal it is to be plated with, which has a positive charge. The positively charged metallic ions are attracted to the negatively charged part and once they come into contact with the part they revert back to their metallic form again. The part is removed from the solution and left to cool.

    To ensure a good quality finish after chrome plating a part must be moulded to a very high quality. Any defects that are on the surface of the part after injection moulding will stand out after plating. Also, any stresses in the moulded components will show up as a defect when chrome plated. Unlike other finishing methods chrome plating does not fill in scratches or other defects. Instead the chrome will form a thinner layer over the defects and, in effect, magnify the problem. For this reason rigorous quality checks are carried out on all products so that money is not wasted plating a part that has a defect.
Source: http://www.finishing.cоm
Last Updated on Tuesday, 08 December 2009 05:53