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铁道科学与工程学报

JOURNAL OF RAILWAY SCIENCE AND ENGINEERING

Vol. 17    Special 1    November 2007

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Process of pulse electrodeposition nanocrystalline chromium fromtrivalent chromium bath
HE Xin-kuai(何新快)1, 2, QIU Guan-zhou(邱冠周)1, CHEN Bai-zhen(陈白珍)1,
ZHOU Ning-bo(周宁波)1, WU Lu-ye(吴璐烨)2, XU Li-jian(许利剑)

1. School of Resources Processing and Bioengineering, Central South University, Changsha 410083, China;
2. School of Packaging and Printing, Hunan University of Technology, Zhuzhou 412008, China

Abstract:Nanocrystalline chromium coating was prepared by pulse electrodeposition from trivalent chromium bath containing carboxylate-urea as complexing agent. The effects of electrodeposition parameters such as current density, bath temperature and solution concentration on the thickness and electrodeposition velocity of Cr deposited films were investigated. The crystallographic structures, morphology and chemical composition of Cr deposited films were analyzed by means of XRD, SEM and EDS. The results indicate that the deposited films with thickness up to 11.2 µm possess a smooth and clean appearance, and the grain size is less than 100 nm. The coating is pure chromium and the Cr deposit has face-centered cubic (fcc) structure and exhibits a (210) growth preference. Both the electrodeposition velocity and thickness exist maximum under different concentration complex agents, ureas, acetates, different temperatures and current densities. Compared with direct current electrodeposition, the thicker coating and finer grains can be obtained at lower temperature and current density by pulse electrodeposition. The electrodepostion velocity is about 0.24 µm/min, which is faster than that by direct current electrodeposition. In 1 mol/L H2SO4, 3.5% NaCl and 10% NaOH solution, corrosion potential of Cr pulse-deposited film is about 100 mV higher than that of direct current. Corrosion and passivation current densities are lower and the nanocrystalline exhibits better corrosion resistance.

 

Key words: pulse electrodeposition; trivalent chromium; chromium coating; nanocrystalline

ISSN 1672-7029
CN 43-1423/U

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