Electrodeposition of crack-free and amorphous Ni-Mo alloys with high Mo content from gluconate baths

Abstract

In this article, electroplated Ni-Mo alloys with high Mo content from gluconate baths are presented. Specifically, the influence of current density on the electrodeposition process, which produced crack-free Ni-Mo alloys with high Mo content, was evaluated. Commonly, Ni-Mo electrodeposition is performed in citrate solutions, as citrate ions promote coordination compounds with greater stability compared to mono and bivalent ligands. However, due to the high internal stress caused by Mo in the coating when its content is very high, microcracks are formed along the surface, causing defects in the deposit. Gluconate baths have been proven to produce crack-free alloys, even when current density is high. The deposits were evaluated for chemical composition by Energy-Dispersive X-ray Specrometry (EDS) and surface morphology by electron microscopy using a Scanning Electron Microscope (SEM). Furthermore, the deposition process was evaluated for current efficiency, and a reaction mechanism was proposed based on observations acquired by other authors. The highest Mo content obtained was 43% by weight. The highest current efficiency was 26%, obtained at 30 mA/cm².