期刊
MATERIALS CHEMISTRY AND PHYSICS
卷 308, 期 -, 页码 -出版社
ELSEVIER SCIENCE SA
DOI: 10.1016/j.matchemphys.2023.128305
关键词
Electrodeposition; Galvanic corrosion; Ni -W; Mixed potential; XPS
This study focused on investigating the effects of tungsten (W) content, heat treatment, and grain size on the corrosion behavior of Ni-W coatings. Ni-W coatings with varying W contents were electrodeposited using pulse and pulse reverse techniques. The coatings were characterized after heat treatment, and corrosion performance was evaluated through potentiodynamic polarization tests. The results indicated that as-deposited coatings had superior corrosion resistance compared to heat-treated coatings, and the corrosion behavior was explained by factors such as surface composition and micro-galvanic corrosion.
In this study we focus on understanding the influence of tungsten (W) content, heat treatment and grain size on the corrosion behaviour of Ni-W coatings. Using pulse and pulse reverse electrodeposition techniques, Ni-W coatings with different W contents (3, 7.5, 12, 17, 20 and 25 at.%) were deposited from a standard ammonia-citrate bath. Coatings were heat treated at 700 degrees C in vacuum for 1 h and then characterized to determine the surface morphology, grain size, and phase transformations. To evaluate the corrosion performance of the coat-ings, potentiodynamic polarization tests were performed in 0.6 M NaCl solution. Polarization test results indi-cated that as-deposited Ni-W coatings had better corrosion resistance compared to heat treated coatings. In the as-deposited condition, corrosion resistance increased up to 17 at.% W. However, further addition of W decreased the corrosion resistance due to high volume fraction of triple junctions and intercrystalline regions. On the other hand, heat treated coatings suffered from micro-galvanic corrosion due to the precipitation of Ni4W and NiW phases, and therefore showed higher corrosion rates compared to as-deposited coatings. The changes observed in the corrosion behaviour of as-deposited and heat treated Ni-W coatings were rationalized based on surface composition, mixed potential theory, and triple junction corrosion theory.
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