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Please use this identifier to cite or link to this item: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/48244

Title: Electrodeposition of black chromium-cobalt alloy based on trivalent sulfate electrolyte
Authors: Hung-Hua Sheu
Chen-En Lu
Hung-Bin Lee
Nen-Wen Pu
Po-Fan Wu
Sheau-Hwa Hsieh
Ming-Der Ger
Contributors: 國立臺灣海洋大學:光電與材料科技學系
Keywords: Trivalent chromium
Black coatings
Date: 2016-01
Issue Date: 2018-08-20T03:49:13Z
Publisher: Journal of the Taiwan Institute of Chemical Engineers
Abstract: Abstract: This study is aimed to improve the corrosion resistance, adhesion strength, and color of trivalent black chromium coatings on steel substrates by using chromium sulfate bath and chromium chloride bath. The effects of the electrodeposition current density on the trivalent black chromium coatings were studied. Surface morphology and chemical composition of coatings have been investigated using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) techniques. The protective behavior from substrates of trivalent black chromium coatings was studied in (3.5 wt. % NaCl) solution by potentiodynamic polarization technique. The better protective behavior from substrates was shown by coatings that formed in chromium sulfate bath. The coatings deposited at low current densities (10 A/dm2) showed high cobalt content because cobalt is more easily reduced than chromium on a cathode. The enhancement of the driving force caused chromium and cobalt to change into oxides and hydroxides when current density increased to more than 30 A/dm2. The best homogeneity of the black color, the degree of blackening and the protective behavior from substrates of coatings occurred at current density 50 A/dm2. The results of XPS indicated that the coatings contained not only chromium oxides and hydroxides but also cobalt oxides and hydroxides. Of all the constituent compounds, Co3O4 was the most dominant in influencing the degree of blackness.
Relation: 59 pp.496-505
URI: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/48244
Appears in Collections:[光電科學研究所] 期刊論文

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