Effect of nickel particles on the interfacial adhesive strength between a Ni-P composite coating and a polymeric composite substrate

• Proposed a method to improve the adhesion strength of composite coating.
• Improved adhesion strength by 99.4% through this method than traditional ones.
• A transition layer containing reinforced particles was added on the composites.
• The influenced of composite surface roughness to adhesion strength was studied.
• The content and size of the particles in the transition layer was studied.

A nickel-rich transition layer is added into the interface between the composite and the metal coating, aiming to enhance the interfacial adhesive strength between the coating and the substrate. When the Ni particle content exceeds 30% of the interface mass, the electroless plating can be carried out without involving palladium activation. The effect of nickel particles and composites roughness on the adhesion strength was investigated. The process consists of the following steps: (1) curing the FRP composites with nickel particles, (2) micro-roughening the composite surface, (3) carrying out acid activation of the composites, (4) conducting the electroless deposition of Ni-P coating. The results show that adding nickel particles is an effective technique to significantly improve the interfacial adhesive strength between the coating and the substrate of the metallized FRP composites. The roughness of composite surface, the particle size and the content of nickel particles are critical factors to affect the adhesive strength and the electroless plating process.