Preparation and corrosion resistance of electroless Ni–P coatings on B4C/Al composite

This study optimizes the electroless nickel plating process on B 4 C/Al composites and clarify the growth and failure mechanisms of the coating. Through orthogonal optimization of the plating solution composition, a high-performance amorphous coating with 11.4 wt% phosphorus content was obtained. At the optimal deposition temperature of 85 °C, the electroless Ni-P coating exhibits accelerated corrosion resistance with the lest corrosion current density of 1.8 μA/cm 2 and corrosion area ratio of 1.07%. A two-stage "nucleation-thickening" growth model is proposed. Nickel preferentially nucleates on the catalytic matrix and encapsulates laterally the inert B 4 C/Al particles to form a dense layer. During immersion corrosion, corrosive solution penetration triggers a strong galvanic reaction at the interface. The accumulation of corrosion products generates significant internal stress. The failure mechanism depends on the competition between this stress and the interfacial bonding strength. Blistering and delamination occur when the stress exceeds the adhesion limit.