Effect of Trisodium Citrate on the Electro-Crystallization of Electrodeposited Ni-Cu-Mo Alloy Coatings

The effect of trisodium citrate on the electrodeposition of nickel-copper-molybdenum in sulfate solution was explored in this paper. According to the results of the nickel-copper-molybdenum electrodeposition experiment, adding a certain amount of trisodium citrate into the electrodeposition solution inhibited the hydrogen precipitation reaction and accelerated the crystallization process on the plated surface to a certain extent, thereby improving the cathodic current efficiency. However, no change occurred to the nucleation mode in the process of electrodeposition crystallization, and it was consistent with the theoretical value of instantaneous nucleation before the peak current (t/t m ≤ 1) was reached. The theoretical values of instantaneous nucleation were consistent. The epitaxial growth rate constant K * of the crystals was reduced after the addition of trisodium citrate into the electrodeposition solution, indicating the inhibitory effect of trisodium citrate on the growth of crystals in the electrodeposition solution. The diffusion coefficient of the nickel-copper-molybdenum ligand ions was reduced as well, suggesting the inhibitory effect of adding trisodium citrate into the plating solution on the cathodic mass-transfer process, which is conducive to promoting its cathodic polarization. Meanwhile, the growth rate of crystals was significantly affected by the applied potential.