Abstract:Two types of Ni-Co-P coatings were synthesized by electroless deposition on p-type Si (100) substrates. Microstructures and properties of the coatings were studied and compared. A mixture of amorphous and nanocrystal structures was found in Ni48Co46P6 coatings, while Ni22Co74P4 coatings contained a nanocrystalline hexagonal closed packed phase with a strong (0002) texture. Surfaces of both coatings were composed of clusters. In Ni48Co46P6 coatings, the clusters were 0.2 ~ 3.5 μm nodules that distributed uniformly, whereas in Ni22Co74P4 coatings there were nano-sized shuttle clusters mixed with micro-sized bud clusters. Both coatings exhibited activation-passivation-transpassivation processes in 3.5% NaCl solution, and Ni48Co46P6 coatings showed a better corrosion resistance. However, corrosion resistance of both Ni-Co-P coatings was decreased remarkably in 1.0% H2SO4 solution. Compared with Ni48Co46P6 coatings, Ni22Co74P4 coatings showed a much improved saturation magnetization and coercivity with a slightly decreased electrical conductivity.