Effects of current frequency on the structural characteristics and corrosion property of ceramic coatings formed on magnesium alloy by PEO technology
✍ Scribed by Guo-Hua Lv; Huan Chen; Wei-Chao Gu; Li Li; Er-Wu Niu; Xian-Hui Zhang; Si-Ze Yang
- Publisher
- Elsevier Science
- Year
- 2008
- Tongue
- English
- Weight
- 799 KB
- Volume
- 208
- Category
- Article
- ISSN
- 0924-0136
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✦ Synopsis
Plasma electrolytic oxidation (PEO) process was carried out on magnesium alloy with a pulsed direct current (dc) power source at high and low frequencies. The morphology and phase composition of the coatings were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The corrosion performances of the different coatings were evaluated via a three-electrode system in a 3.5-wt.% NaCl solution. It was detected that the PEO coatings were mainly composed of MgF 2 and Mg 3 (PO 3 ) 2 phase. Coatings produced at relative high frequency had smaller pore size and looked much denser than those at low frequency.
As a result, they performed better corrosion resistance in the present corrosive solution.
These experimental results could be ascribed to the formation mechanism of the PEO coatings: lower frequency provided longer time for one single pulse, which induced continuous discharge.