[en] Electroless nickel-boron (NiB) coatings and duplex electroless nickel-phosphorous/nickel-boron (NiP/NiB) coatings can provide protection against corrosion to steel and aluminium alloys substrates.
Nickel-boron coatings with a moderate thickness (close to 25 µm) were synthesized directly on steel substrate. Duplex nickel-phosphorous/nickel-boron coatings (with a thin nickel-phosphorous under layer of 5 to 8 µm) were also synthesized on both steel and aluminium alloys.
The systems were characterized by electrochemical methods (potentiodynamic polarization), mainly in aqueous NaCl (0.1 M) but also in other solutions, and by SEM observation after electrochemical tests.
The effects of heat treatment, duplex coating and replenishment during the plating process were observed. Comparisons were made with single layer nickel-phosphorous.
