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Home  >  Journal list  >  MATERIALS TRANSACTIONS  >  Vol.42  No.8 (2001)  >  pp.1691-1699

MATERIALS TRANSACTIONS
<<Previous article Vol.42  No.8 (2001)   pp.1691 - 1699 Next article>>

An Investigation of the Structure and Corrosion Resistance of Permanganate Conversion Coatings on AZ91D Magnesium Alloy

Hiroyuki Umehara1), Matsufumi Takaya2) and Yo Kojima3)
1) Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology
2) Depatment of Precision Engineering, Chiba Institute of Technology
3) Depatment of Mechanical Engineering, Nagaoka University of Technology


Conversion coatings for magnesium have traditionally been based on immersion treatment in the solution containing hexavalent chromium compounds. The excellent performance of these coatings as paint bases has been established in a broad range of application. However, the replaceable surface treatment has been strongly emphasized by present environmental needs to eliminate hexavalent chromium. The development of chemical conversion coatings in permanganate bath on magnesium alloys has been studied using mass gain measurements, measurements of corrosion potential, X-ray diffraction, X-ray photoelectron spectroscopy, glow discharge spectroscopy and microscopic examination. Chemical conversion coatings obtained from HF addition in bath consisted of the film that was composed mainly of manganese oxides and magnesium fluoride. It was found that these films formed amorphous composite coating. Corrosion resistances of permanganate chemical conversion coatings were comparable with that for chromating.


Keyword:
magnesium alloy, chromium-free chemical conversion, conversion film structure, permanganate chemical conversion bath, corrosion resistance

Received: February 14, 2001
Accepted: May 10, 2001 , Published online: September 06, 2005
Copyright (c) 2005 The Japan Institute of Light Metals

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