2007•Electroplating & Pollution ControlRequires access
Study of Silicate and Tungstate Composite Conversion Coatings on Magnesium Alloy
Zhu Jing
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Abstract
A conversion coating formed on magnesium alloy AM60 with a chromate-free bath mainly composed of silicate and tungstate is studied.The effects of tungstate and KMnO_4 on the coating are discussed.The best time,acidity and temperature of reaction are obtained through comparison.The microstructure of the conversion film is observed with scanning electron microscopy.Polarization curves and electrochemical impedance analysis are used to indicate the corrosion resistance of the conversion coating.The microfacies structure of the conversion coating is investigated by X-ray diffraction spectrum,revealing that the film is of noncrystalline structure.The components of the conversion film are analyzed by energy spectrum.On this basis,the growth mechanism of the chemical conversion coating is put forward.