Objective To study the crystallizing characteristics of Ni-4. 11% Mo-6. 50% P and Ni-9. 19% P coatings prepared by chemical deposition during annealing, and to establish the relationship between the microstructure and corrosion resistance by quantitative characterization of crystallization degree, grain size and mass fraction of crystalline phases of the coatings. Methods The structural characteristics of coatings were quantitatively analyzed using XRD diffraction technique and Jade software; the morphology and composition of coatings were determined by SEM / EDS measurements; the corrosion resistance of both coatings was compared by immersion corrosion tests and metallographic microstructural observation. Results When the annealing temperature was below 400 ℃ , only crystallized Ni phase existed in the Ni-Mo-P coating. The crystallization reaction of the Ni3 P phase occurred at 400 ℃ or above, and was accompanied by the formation of Ni-Mo solid solution. When the annealing temperature reached 600 ℃ , the degree of crystallization of the Ni-Mo-P coating was 88. 13% . In contrast, when the precipitation temperature of Ni3 P phase in the Ni-P coating was lowered to 300 ℃ , the degree of crystallization reached 91% at 600 ℃ . The grain sizes of the Ni-Mo-P coating were smaller than those of the Ni-P coating at the same annealing temperature. The grain size of Ni3 P phase was always larger than that of Ni phase at the crystallization reaction temperature of Ni3 P phase. In the 0. 5 mol / L H2 SO4 solution, for the Ni-Mo-P alloy, the heat treatment could significantly improve its corrosion resistance except at the annealing temperature of 300 ℃ . For Ni-P alloy, the as-plated coating had the best corrosion resistance. In the 10% HCl solution, the Ni-Mo-P alloy annealed at the high temperature of 600 ℃ had higher resistance to pitting corrosion. For Ni-P alloy, it showed the opposite trend. The as-plated and annealed coatings at low temperature of 200 ℃ showed the best pitting corrosion resistance. Conclusion The co-deposition of Mo into Ni-P coating enhanced the precipitation temperature of Ni3 P phase and decreased the degree of crystallization and grain size. Compared with the Ni-P coating, the Ni-Mo-P coating annealed at high temperature exhibited better pitting resistance, but the resistance to uniform corrosion in H2 SO4 solution was lower.