Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5362844 | Applied Surface Science | 2009 | 8 Pages |
Abstract
Plasma electrolytic oxidation (PEO) of a ZC71/SiC/12p-T6 magnesium metal matrix composite (MMC) is investigated in relation to coating growth and corrosion behaviour. PEO treatment was undertaken at 350 mA cmâ2 (rms) and 50 Hz with a square waveform in stirred 0.05 M Na2SiO3.5H2O/0.1 M KOH electrolyte. The findings revealed thick, dense oxide coatings, with an average hardness of 3.4 GPa, formed at an average rate of â¼1 μm minâ1 for treatment times up to 100 min and â¼0.2 μm minâ1 for later times. The coatings are composed mainly of MgO and Mg2SiO4, with an increased silicon content in the outer regions, constituting <10% of the coating thickness. SiC particles are incorporated into the coating, with formation of a silicon-rich layer at the particle/coating interface due to exposure to high temperatures during coating formation. The distribution of the particles in the coating indicated growth of new oxide at the metal/coating interface. The corrosion rate of the MMC in 3.5% NaCl is reduced by approximately two orders of magnitude by the PEO treatment.
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Authors
R. Arrabal, E. Matykina, P. Skeldon, G.E. Thompson,