Effect of surfactants on the behavior of the Ni-P bath and on the formation of electroless Ni-P-TiC composite coatings

Abstract

The present study is a systematic investigation into the effect of three different types of surfactants (anionic: SDBS, cationic: CTAB, and non-ionic: PVP) on the behaviour of electroless Ni-P baths containing TiC nanoparticles, and on the formation of Ni-P-TiC composite coatings. The effect of surfactants can be observed in the interfacial phenomena, i.e. wetting and electrokinetic behaviour during the formation of the coating. The wetting properties of the coating bath were investigated by the sessile drop method, which revealed the wetting improvement on all three substrates (W302 steel, TiC, Ni-P coating substrates) in the case of the anionic and cationic surfactant. The Zeta potential measurement showed a stability decrease in Ni-P bath compared to the distilled water medium, which led to the agglomeration of the TiC particles. TiC agglomerate size below 100 nm was achieved by all three types of surfactant (1 g/L) in distilled water; however, only larger agglomerates were measured in the Ni-P bath. Finally, the Ni-P-TiC composite coatings on steel substrate were created. The investigation of the cross-section of the coatings revealed that, the highest amount of TiC (0.53 wt.% and 0.52 wt.%) was incorporated in the Ni-P matrix with the use of 0.1 g/L CTAB and 0.1 g/L PVP respectively, although these particles formed larger agglomerates.