Effect of rare–earth (Ce, La) compounds on the microstructure, mechanical and electrochemical corrosion characteristics of electroplated Ni films

For optimizing the microstructure and performance of Ni–electroplating film, the soluble rare–Earth (RE) compounds CeCl3 or LaCl3 were introduced, which were electrodeposited on Cu substrate by direct current (DC) and pulse current (PC) methods, respectively. The surface characteristics of morphology, composition, and phase of obtained different deposits were investigated, and the relationship between the structure and the performance of internal stress, hardness, and electrochemical responses was discussed. The results show that both RE compounds were conducive to eliminating the surface pits by inhibiting the hydrogen evolution reaction, while did not co–deposit into the Ni film. Moreover, the preferred orientation of Ni (111) crystalline plane was altered into Ni (200) by LaCl3, and its combination with PC–electrodeposition further had a better grain refinement effect than CeCl3. Due to the formation of a relatively dense and fine deposit, the PC–electrodeposited Ni/LaCl3 film exhibited the highest hardness of 320 HV, lowest tensile stress of 55 MPa, and best electrochemical passivation protection, which effectively improved the comprehensive performance of Ni film and demonstrated a good prospect for industrial applications.