The Department of Defense (DoD), Solar, Aerospace and Automotive Industries have all required black coatings for the sole need of light and energy absorption. Up until recently, the primary solutions were to use metal conversion coatings and or organically electrolytic processes to darken a part’s surface. Those coatings typically used were black oxide, phosphate, chromates, molybdates, and metal impurities such as the addition of zinc and iron added to plating baths like chrome, nickel, and zinc. Electroless nickel has now been chosen to be the best of all worlds for its inherent corrosion protection and ability to be adequately blackened to near 100% light absorption.
Due to higher demand in today’s market place to have equipment and parts be aesthetically or functionally black and survive in harsher climates longer than what was previously accepted, electroless nickel is now the proven and industry wide accepted process drop-in replacement. The ability to create black electroless nickel is a challenge and is widely believed to be a proprietary secret. Companies like Rockwell Collins experimented for decades to find a reproducible way to create fully functional black electroless nickel coatings. Some approaches were to bake the coating in a non-inert atmosphere to cause the phosphor in the nickel alloy to oxidize into a bluish-purple to almost black film on the surface of the part. That proves to be rather non-uniform at best. Others tried to add impurities to the electroless nickel bath like that of a black electrolytic nickel plating bath. That too proved unsuccessful. Basically it comes down to a host of conditions during and after the electroless nickel plating that allows the coating to be blackened.
Sharretts Plating Co., Inc. (SPC) has from its own experience and laboratory work figured out the optimal means to create a black electroless nickel coating. Using high purity lab grade reagents and honing in the optimal bath parameters, SPC is fully capable of reproducing high volumes of work load through our black electroless nickel process. We call it “SMITH-EN-BLACK™” named after our top laboratory and chief environmental officer. This name comes from a funny anecdote where Mr. Smith was plating ceramics and during the process he managed to metallize his forefinger which turned black from briefly touching the top of the electroless nickel solution while removing a PZT (Lead-Zirconate-Titanate) wafer. His finger print remained black for several days.
What is “SMITH-EN-BLACK ™?” SMITH-EN-BLACK ™ is a low phosphorous coating and has a minimum thickness equal to or greater than 500µ” (13µm). The process can be enhanced to create superior corrosion protection by utilizing duplex electroless nickel coatings with 10-13% phosphorous as the first coating layer under our SMITH-EN-BLACK™ coating. Parts weighing up to a half ton can be processed through our black electroless nickel line. This coating is now fully available to our general customer base starting as of March 31, 2011. Please contact SPC at your earliest convenience to learn if your parts are a candidate for SMITH-EN-BLACK™.