Preparation and Properties of Textured Ni-W Coatings Electrodeposited on the Steel Surface from a Pyrophosphate Bath

Ni-W alloys with a (2 2 0) or (1 1 1) preferred orientation growth and amorphous structure were prepared from a pyrophosphate bath using the electrodeposition method. Structure transformation can be the result of the bath temperature (Tb) and the concentration of sodium tungstate (CW) in the bath. Increasing the Tb and CW can change the crystal growth from (2 2 0) to (1 1 1). At a higher Tb and CW, an amorphous Ni-W alloy can be obtained. The tungsten content in the coatings should be responsible for the structure change. The three textured Ni-W alloys with a (2 2 0) texture, (1 1 1) texture and amorphous structure were annealed at different temperatures ranging from 200 to 700 & DEG;C. The microhardness, corrosion resistance and HER of the as-deposited and annealed Ni-W alloys were comparatively studied. The results show that the microhardness of the amorphous Ni-W alloy is the highest and reaches 1028 HV after annealing at 400 & DEG;C. The (2 2 0)-textured Ni-W alloy has the best corrosion resistance, which is further improved after annealing, while the HER activity of the (1 1 1) textured Ni-W alloy is superior.