Electroplating, Electroless Nickel and Chromium Plating
Electroplating is a process in which the parts to be plated are connected to a negative terminal - the cathode (DC source) - and a positive pole known as the anode. Electroplating can be used to apply decorative layers to improve resistance to corrosion and abrasion such as nickel and chromium on steel. Chromium deposits in decorative applications are applied as thin coatings over thicker nickel surfaces. Decorative plated parts include hand tools, office products and pen clips. Plating thicknesses can be in tenths, or in the case of chromium on nickel (flash), in millionths. Lot sizes can vary from 1 to 10,000 pieces on up to 16" x 36" racks.
Hard Chromium deposited on a shaft to effect wear resistance is another example of electroplating. Hard chromium deposit thicknesses can be from 0.00002" to 0.035"+ on steel, brass, copper, and any alloy of these metals. In addition to corrosion protection and wear resistance properties, chrome provides bright surfaces. The use of hexavalent chrome, recognized as the "old-fashioned true chrome" is still used by full-line plating specialists.
Electroless Nickel deposits come about through a process that continues once it is started (autocatalytic). It is similar to electroplating, but without outside current. The metal ions are reduced by chemicals in the plating solutions. The electroless process is suited for nonmetallic parts or metallic substrates when a uniform coating is required on irregularly shaped articles. Electroless nickel deposits are generally harder, more brittle and more uniform than electroplated deposits. Hardness values should fall in the range from 60 - 64 Rc. Thickness can be from 0.00005" to 0.004", applied by rack or barrel.
Platers should be able to meet AMS, OEM, and military specifications in addition to being environmentally in compliance. Other processing capabilities to be considered by companies in the plating business are the baking of plated parts, buffing, vibratory finishing and hand polishing. Added factors to be evaluated when reviewing plating sources are their lifting capacity, maximum material length capabilities and maximum solution depth.
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