Electrolesspinnoitus

Electrolesspinnoitus, or electroless plating, is a chemical deposition process that coats a substrate with a metal without applying external electrical current. The coating forms through a spontaneous redox reaction in an aqueous bath, where metal ions are reduced to metal on the surface. Once a catalytic surface is present, deposition proceeds autocatalytically and can occur uniformly on complex geometries and recessed areas.

Common chemistries include electroless nickel phosphorus (Ni-P) and electroless nickel boron (Ni-B) coatings. Nickel-cobalt, copper, silver, and related alloys are also used in specialized applications. Ni-P baths typically use hypophosphite as the reducing agent and yield coatings containing roughly 4–14% phosphorus, which can be hardened by subsequent heat treatment. Ni-B coatings incorporate boron (about 1–3%) and can achieve very high hardness, though they may be more brittle. Copper-based electroless baths are emphasized for seed layers in printed circuit boards and for corrosion protection in various components.

Process and preparation involve substrate cleaning and activation to create a catalytic surface, often using sensitization and palladium or alternative methods for non-oxide substrates. Bath conditions are typically alkaline for Ni-P, with temperatures around 85–95 °C; deposition rates are moderate and depend on bath composition, pH, and temperature. Post-deposition heat treatment can modify hardness, wear resistance, and corrosion behavior.

Applications include corrosion- and wear-resistant coatings for mechanical parts, electrical components such as PCB seed layers, and functional coatings where uniform coverage is required. Benefits include conformal coating of complex shapes and independent of geometry, while limitations include slower deposition rates, bath maintenance, and environmental considerations related to nickel compounds.