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URN etd-0722113-145110 Statistics This thesis had been viewed 1776 times. Download 170 times. Author Ming-Han Hsieh Author's Email Address No Public. Department Materials Engineering Year 2012 Semester 2 Degree Master Type of Document Master's Thesis Language zh-TW.Big5 Chinese Page Count 115 Title Effects of different electrolytes on the properties of bipolar pulsed micro-arc coatings on ADC12 aluminum alloys Keyword Al-Si alloy Micro-arc Oxidation Micro-arc Oxidation Al-Si alloy Abstract This research is to investigate the effect of different electrolytic solutions on the oxide coatings of ADC12 aluminum alloys by bipolar pulse micro-arc oxidation (MAO) process at current density 6A/dm2. The electrolytes were used various additions of NH4VO3, (NaPO3)6 and ZrO2 to the Na2SiO3 and NaOH solutions. The morphologies, composition and microstructure of MAO coatings were investigated by SEM、XRD、XPS and CSM TRIBOMETER. Corrosion resistance of the coatings was evaluated by Polarization curves.
Results showed that the oxide coatings formed in the electrolyte containing ammonium metavanadate appeared the color of yellow-green due to coating composition of V2O3, V2O5. The best compactness and corrosion resistance of MAO coatings was found in the elctrolyte with ammonium vanadate for charging ten mintes. The surface roughness of the coatings decreased, the hardness increased, and corrosion resistance slightly decreased as sodium hexametaphosphate added to ammonium vanadate electrolyte for micro-arc oxidation. ZrO2 addition to electrolytes improved the the properties of the coatings such as increasing surface hardness, deceasing roughness and slightly increasing coating thickness, but the corrosion resistance slightly decreased under the addition to ammonium vanadate electrolyte and slightly increased under the addition to sodium hexametaphosphate solution. However, there was little effect on the corrosion resistance of the coatings for ZrO2 additions.
Advisor Committee Chia-Jung Hu - advisor
Chiu-Lung Li - co-chair
Mu-Rong Yang - co-chair
Files Date of Defense 2013-05-27 Date of Submission 2013-07-22