electrolessnikkelipinnoitus

Electroless nickel plating, known in Finnish as electrolessnikkelipinnoitus, is a chemical bath deposition technique that deposits a uniform, non‑electrically conductive layer of nickel onto conductive substrates without the use of an external electrical power source. The process relies on a self‑sustaining autocatalytic reaction in which a reducing agent, commonly sodium hypophosphite, reduces nickel ions in solution to metallic nickel, while a catalyst such as palladium or platinum initiates the reaction on the substrate surface.

The resulting nickel coating is typically 20 to 200 µm thick, depending on bath conditions and deposition time. It is known for its excellent hardness, corrosion resistance, and wear resistance, thanks to the alloying of phosphorus (generally 5–15 wt %) into the metal matrix. This phosphorus‑rich electroless nickel provides a tougher surface than electrolytic nickel, which lacks phosphorus.

Applications of electroless nickel plating span aerospace, automotive, electronics, medical devices, and hard‑facing production. It is especially valued for complex geometries, internal channels, or parts that cannot be fed through a power‑driven electrolytic unit. The coating is also compatible with shot‑peening, ion‑beam modification, and subsequent electroplating.

Compared with electroless tin or copper plating, the nickel variants offer higher temperature stability and stronger adhesion to metals such as steel, aluminum, and composites. However, the process requires careful control of bath pH and temperature to maintain uniform deposition and avoid defects such as discoloration or peeling.