Corrosion resistance of nanocrystalline Mg–Cr alloys deposited by magnetron sputtering |
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Authors: | Meilutė Samulevičienė Povilas MiečinskasKonstantinas Leinartas Asta GrigucevičienėPutinas Kalinauskas Vitalija JasulaitienėRemigijus Juškėnas Eimutis Juzeliūnas |
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Affiliation: | Centre of Physical Sciences and Technology, Institute of Chemistry, A. Goštauto 9, 01108 Vilnius, Lithuania |
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Abstract: | Nanocrystalline Mg–Cr alloys were formed by dc magnetron sputtering in a wide range of concentrations. Structure, composition and grain sizes of the deposits were studied by XRD and XPS. EIS and dc-voltammetry showed that small chromium concentrations (2–8 at.%) had detrimental effect, while high corrosion resistance was observed when chromium content reached one third or so. Chromium refinement effect on alloy crystalline structure was found by XRD. The values of grain sizes were determined as follows: Mg–3Al (chromium-free) – over 100 nm, Mg–2Cr – 60.5 nm, Mg–8Cr – 44.6 nm, Mg–20Cr – 31.0 nm, Mg–45Cr, Mg–53Cr – ∼11.0 nm and ∼15 nm for sputtered Cr. Mott–Schottky plots showed that the spontaneous oxide layers formed on the alloys with high Cr content (Mg–36Cr, Mg–53Cr) were highly doped semiconductors of n-type. A conductivity change n–p was observed at E = 0.0 V (Ag/AgCl) in a buffer solution (pH 9.9). The conductivity change was also confirmed by photo-electrochemical measurements. Surface enrichment by chromium during initial stages of corrosion was determined, which promote corrosion resistance and provides an opportunity of surface auto-protection (self-healing) in damaged locations. |
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Keywords: | Magnesium Chromium Alloys Sputtering Semiconductor EIS XRD XPS |
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