Nickel-plating technique, electroless

In one electroless plating technique, which reportedly achieves attenuation levels of 70 dB in layers of 1-2 microns thick, the molded part is immersed in an aqueous solution of copper salt, reducing agent, and initiator to obtain copper deposition as the primary shielding layer. Nickel is then added to form an outer layer that provides corrosion resistance and improved impact strength. 

Copper and nickel were successfully coated using electroless plating techniques to give excellent penetration of the tows with a uniform deposit, but the method proved to be too expensive. 

In a selective electroless plating, a conductive film of copper or nickel is deposited onto a specific part of the molding as opposed to overall plating by conventional techniques that require paint finishing. Attenuation levels of 50 dB can be obtained at layers of 1-3 microns. 

The electroless deposition technique has a special application in the chromium plating of plastics, particularly for automobiles. A primary nickel coating is nsed to obtain the conducting layer necessary for the subsequent electrodeposition of chrominm or other metals. A common practice is to coat the electroless Ni first with Cu, then with more Ni and finally with very thin Cr, all by electroplating techniques. 

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