Synthesis, characterization and applications of nanostructured Ni-W alloys with good corrosion resistance and high hardness

Abstract

The aim of the chapter is to study in detail the effect of the different pulse programs on the chemical composition, nanostructure, catalytic properties, and corrosion resistance of Ni-W alloys deposited on steel from citrate-containing baths. The results indicate the formation of Ni-W hard and ductile nanostructured coatings where two different phases are observed in the bulk structure: a W-rich amorphous phase and a Ni-rich crystalline phase. The surface of the coatings consists of nano-sized crystals forming a cauliflower-like structure protected by a mixture of nickel and tungsten oxides. The cauliflower structure is preserved into the bulk coating. The composition and morphology of the surface defines if the alloys may act as HER (hydrogen evolution reaction) catalysts or be corrosion resistant in neutral media containing sulfate anions. Ni-W nanostructured coatings were functionalized by tetraethoxysilane (TEOS) and octadecyltrichlorosilane (OTS) in a two-step procedure making the surface hydrophobic and suitable for further applications.