Electroless Nickel Plating – Applications, Process and More
Electroless nickel plating is specified in a wide variety of applications to provide corrosion and wear resistance. Grooves, slots, blind holes, threads, and even the inside of tubing will have the same coating thickness. The coating uniformity of the electroless nickel process helps maintain tight tolerances on threaded fasteners. Such coatings also help fight corrosion and eliminate galling of the threads during use as well as extend service life.
Applications for electroless nickel plating in the aerospace industry are not limited to engine components. The coatings help protect airframe assemblies such as landing gear components, ramp-locking systems, and flap and actuator components from corrosion and wear. Electroless nickel (EN) plating is also known as chemical or auto-catalytic nickel plating. In contrast to the electroplating (galvanic) technique, EN plating baths work without an externally applied electric current.
The plating operation is based on the catalytic reduction of nickel ions onto suitable substrates. The EN process deposits uniformly hard coatings on any section of a part exposed to the fresh plating solution. Grooves, slots, blind holes, threads, and even the inside of tubing will have the same thickness of the coating.
The EN plating process is, however, more than just dunking parts into a plating bath. In fact, the plating tank is only one component in a sequence of processing steps. Bath chemistry and composition play an important role during the EN plating process. But other considerations contribute equally to coating success.
Parts undergo mechanical finishing operations to improve surface finish or to remove gross surface contamination, such as mill scale or weld slag. Vibratory deburring, blasting and tumble finishing improve the surface condition and let the EN plating perform better. Shot-peening not only improves finish but may also serve to redistribute localized stresses arising from machining and fabrication processes. Components made from unusual or difficult-to-plate alloys require chemical pretreatment to ensure the EN coating has adequate initiation, adhesion, and quality.
The best plating process is one that prioritizes all requirements such as the primary and secondary functions of the coating and the environment it must withstand. These parameters help the coating house establish a well-thought-out sequence of preplating, plating, post-plating, and testing processes.