Understanding corrosion via corrosion product characterization: II. Role of alloying elements in improving the corrosion resistance of Zn–Al–Mg coatings on steel |
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Authors: | P Volovitch TN Vu C Allély A Abdel Aal K Ogle |
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Affiliation: | aSurface Engeneering Team, LPCS, CNRS UMR7045, Ecole Nationale Supérieure de Chimie de Paris, 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05, France;bArcelorMittal Research SA, 57283 Maizières-lès-Metz, France |
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Abstract: | Corrosion products are identified on Zn, ZnMg and ZnAlMg coatings in cyclic corrosion tests with NaCl or Na2SO4 containing atmospheres. For Mg-containing alloys the improved corrosion resistance is achieved by stabilization of protective simonkolleite and zinc hydroxysulfate. At later stages, the formation of layered double hydroxides (LDH) is observed for ZnAlMg. According to thermodynamic modeling, Mg2+ ions bind the excess of carbonate or sulfate anions preventing the formation of soluble or less-protective products. A preferential dissolution of Zn and Mg at initial stages of corrosion is confirmed by in situ dissolution measurement. The physicochemical properties of different corrosion products are compared. |
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Keywords: | A Metal coatings A Zinc A Aluminium A Magnesium C Atmospheric corrosion C De alloying |
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