期刊
APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING
卷 128, 期 2, 页码 -出版社
SPRINGER HEIDELBERG
DOI: 10.1007/s00339-021-05239-5
关键词
AZ91 magnesium alloy; PEO coating; Polydimethylsiloxane; Corrosion resistance
资金
- Yekta Mobaddel Pars Co.
To improve the corrosion behavior of a magnesium alloy, a two-step coating process involving plasma electrolytic oxidation coating (PEO) and the immersion method was used. The PEO coating contained different phases, while the PDMS coating formed a non-porous layer. The corrosion tests showed that the PEO/PDMS hybrid coating effectively reduced the corrosion rates of the magnesium alloy.
To improve the corrosion behavior of a magnesium alloy, two-step coatings have been fabricated through plasma electrolytic oxidation coating (PEO) under constant voltage conditions applied to the AZ91 substrate surface in the silicate electrolyte. A polymeric layer [Polydimethylsiloxane (PDMS)] has been successfully implemented by the immersion method on both bare AZ91 alloy and pre-treated samples by the PEO process. PEO coating contains MgO, MgSiO3, and Mg2SiO4 phases detected by X-ray diffraction patterns (XRD). The surface morphology observation investigated using the field emission scanning electron microscopy (FESEM) showed a porous and non-porous layer on the substrate for PEO and PEO/PDMS coatings, respectively. The topography and roughness of the PEO coating evaluated by atomic force microscopy (AFM) revealed a high roughness for the PEO coating. The chemical composition of coatings was determined using X-ray energy distribution spectroscopy (EDS), and the corrosion behavior of the AZ91 substrates with/without coating was studied by the potentiodynamic polarization test in the Ringer solution. The results showed that the corrosion (E-corr) potential of the AZ91 substrate increased compared to a single-layer PDMS coating from - 1.48 to - 1.47 V, and their corrosion current density (i(corr)) reduced from 4.3 to 0.486 mu A center dot cm(-2) in the order given. However, by applying PEO coating as a pre-treatment utilizing the PEO/PDMS composite coating, these values were obtained - 0.75 V and 0.9 nA center dot cm(-2), respectively. So, applying PEO/PDMS hybrid coating may effectively reduce the high corrosion rates of magnesium alloys as the main limitations in the physiological environment.
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