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Preparation and corrosion resistance of Ni‐P bilayer on magnesium alloy
Author(s) -
Yuan J.,
Gao Y.,
Wang J. H.,
Hu W. B.
Publication year - 2017
Publication title -
materials and corrosion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.487
H-Index - 55
eISSN - 1521-4176
pISSN - 0947-5117
DOI - 10.1002/maco.201709515
Subject(s) - bilayer , corrosion , materials science , nanocrystalline material , amorphous solid , layer (electronics) , diffractometer , metallurgy , plating (geology) , magnesium alloy , alloy , scanning electron microscope , x ray photoelectron spectroscopy , chemical engineering , composite material , crystallography , chemistry , membrane , nanotechnology , biochemistry , geophysics , geology , engineering
Ni‐P bilayers were prepared on AZ61 magnesium alloy by electroless plating method in dual baths with pH value of 11.0 and 5.5. The thickness, surface morphology, composition, structure and corrosion resistance of Ni‐P bilayer were observed and determined by scanning electron microscope (SEM), energy dispersive X‐ray spectrometry (EDX), X‐ray diffractometer (XRD) and electrochemical workstation. The results show that Ni‐P bilayer is composed of inner layer in mixed amorphous and nanocrystalline structure with phosphorus content of 3.9–4.0% and outer layer in amorphous structure with phosphorus content of 8.8–10.9%. The plating time of inner layer has a great impact on the morphology and corrosion resistance of Ni‐P monolayer and bilayer, and the corrosion resistance of Ni‐P bilayer is obviously higher than that of inner layer. The optimum plating condition for Ni‐P bilayer is the combination of inner layer's plating time of 30 min and outer layer's plating time of 180 min, under which Ni‐P bilayer gets a dense structure, smooth surface and higher corrosion resistance than that of single inner layer and outer layer.