[en] Electroless nickel plating involves the deposition of a metallic-metalloid alloy layer on substrate by electrochemical reactions in aqueous solution without the need of external current. Electroless nickel deposits possess interesting properties such as uniform thickness, good adhesion, high hardness, wear resistance, good corrosion resistance. There are two major classes of electroless nickel coatings depending on the reducing agent used: nickel-phosphorous (Ni-P) and nickel-boron (Ni-B). Ni-B coatings are known to be smooth, hard and wear resistant, but have moderate corrosion resistance compared to Ni-P layers that are known to provide better corrosion resistance, but lower mechanical properties. The formation of duplex Ni-B/Ni-P coatings or multilayers Ni-B/Ni-P could be a good compromise for all those properties: Duplex coatings with a Ni-B layer at the top are the best candidate in as-plated conditions and multilayers coatings present better wear resistance than monolayers and good corrosion resistance with a medium hardness.
