| 1. |
- Sieber, Maximilian, et al.
(author)
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Corrosion Protection of Al/Mg Compounds by Simultaneous Plasma Electrolytic Oxidation
- 2015
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In: Materials Today: Proceedings, Volume 2, Supplement 1. - : Elsevier Ltd. ; , s. S149-S155
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Conference paper (peer-reviewed)abstract
- The application of Al/Mg compound materials for lightweight structures is limited by their corrosion susceptibility. The primary corrosion attack takes place at the Mg component. This may partly be caused by galvanic corrosion and partly by the insufficient formation of a natural passive layer on magnesium. Therefore, oxide coatings were produced on the co-extruded Al/Mg compounds by simultaneous plasma electrolytic oxidation (PEO). A silicate-alkaline and a silicate-phosphate-alkaline electrolyte were used for the coincident production of coatings with a thickness of several 10 microns on both the aluminum and the magnesium component. The inherent flaws of the coating (pores, cavities) allow for the infiltration with an epoxy-based sealant. The electrochemical behavior of the magnesium component covered with the oxide coatings with and without sealing was compared with reference to the unmodified surface. The surface modification (PEO w/wo sealing) significantly decreases the corrosion susceptibility of the Mg component, and thus of the compound.
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| 2. |
- Sieber, Maximilian, et al.
(author)
-
Wear-resistant coatings on aluminium produced by plasma anodising - A correlation of wear properties, microstructure, phase composition and distribution
- 2014
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In: Surface & Coatings Technology. - : Elsevier. - 0257-8972 .- 1879-3347. ; 240, s. 96-102
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Journal article (peer-reviewed)abstract
- In the recent decades, various process windows have been found for plasma anodising of aluminium surfaces to produce wear-resistant alumina coatings. The coatings offer a high hardness and provide an excellent bonding to the substrate material, thus preventing spallation under mechanical or tribological load. In the present study, coatings with a high abrasive wear resistance and a hardness of up to 12GPa were produced in an electrolyte of 5g/l sodium metasilicate and 5g/l potassium hydroxide at a current density of 30A/dm2. To understand the reasons for the high wear resistance, the morphology as well as the phase composition and distribution within the coating were examined globally and locally using X-ray diffraction with conventional and grazing incidence and electron backscatter diffraction. The analyses show that the coating globally is comprised of approximately one third of α-alumina, one third of γ-alumina and one third of amorphous alumina with locally varying phase content.
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