scholarly journals PLASMA ELECTROLYTIC OXIDATION COATING ON 6061 AL ALLOY USING AN ELECTROLYTE WITHOUT ALKALI IONS

2018 ◽  
Vol 54 (5A) ◽  
pp. 151 ◽  
Author(s):  
Quang Phu Tran
Keyword(s):  
Corrosion Resistance ◽  
Oxide Layer ◽  
Plasma Electrolytic Oxidation ◽  
Free Alkali ◽  
Al Alloy ◽  
Micro Hardness ◽  
Alkali Ions ◽  
Electrolytic Oxidation ◽  
Plasma Electrolytic ◽  
6061 Al Alloy

Plasma electrolytic oxidation (PEO) technique is well known to use for modifying the surface of valve metal such as Al, Mg and Ti, which improves mechanical and corrosion resistance properties. PEO is an electrochemical process of oxidation by creating micro-discharges on the surface of metal immersed in an electrolyte under applying a high voltage. Electrolyte used in PEO process is almost based on alkali ions such as Na ion. The report on PEO process using free-alkali ion is very rare. In this study, the oxide layer on 6061 Al alloy was produced in a free-alkali ion electrolyte containing calcium phosphate and ammonia water by PEO method. Microstructure, micro-hardness and corrosion resistance of PEO coated were investigated and discussed. Surface morphology analysis indicated the coating characterized by micro-pores, pan-cakes like, and micro-crakes with pore size and percentage of pores on coating surface are smaller than 1 mm and 2.5 %, respectively. Micro-hardness and corrosion resistance of PEO coated are greatly improved compared to the bare Al alloy. Free-alkali-ions in oxide layer coated on Al alloy is important for many applications today.

ffect of Na2WO4 in electrolyte on mechanical properties of oxide layer on Al alloy via plasma electrolytic oxidation

2015 ◽  
Vol 53 (8) ◽  
pp. 535-540 ◽  
Author(s):  
Young Gun Ko ◽  
Dong Hyuk Shin ◽  
Hae Woong Yang ◽  
Yeon Sung Kim ◽  
Joo Hyun Park ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Oxide Layer ◽  
Plasma Electrolytic Oxidation ◽  
Al Alloy ◽  
Electrolytic Oxidation ◽  
Plasma Electrolytic

scholarly journals CHARACTERISTICS OF PLASMA ELECTROLYTIC OXIDATION COATINGS ON 6061 AL ALLOY PREPARED AT DIFFERENT CURRENT DENSITIES

2020 ◽  
Vol 58 (6) ◽  
pp. 699
Author(s):  
Quang-Phu Tran ◽  
Van-Da Dao ◽  
Van-Hoi Pham
Keyword(s):  
Plasma Electrolytic Oxidation ◽  
Current Mode ◽  
Coated Sample ◽  
Al Alloy ◽  
Properties Of Coatings ◽  
Sem Images ◽  
Oxide Layers ◽  
Electrolytic Oxidation ◽  
Plasma Electrolytic ◽  
6061 Al Alloy

Plasma electrolytic oxidation (PEO) has earned much attention due to its powerful and easy formation of hard and corrosion-resistant oxide layers on valve metals, such as Al alloys. Here we report the effects of current density (CD) on microstructure and properties of coatings on 6061 Al alloy by PEO using direct current mode. The electrolyte contains the chemicals of Na2SiO3, Na2WO4´2H2O, and NaH2PO2´H2O. The CDs adopted 5.0, 7.5, 10.0, and 12.5 A/dm2, respectively, for a fixed PEO time of 30 min. The thickness, surface morphology, phase composition, hardness, and corrosion resistance of PEO coatings as the function of the applied CD have been studied and discussed. Studied results show the coating thickness is proportional to the applied CD. When the applied CD increases 2.5 times from 5.0 to 12.5 A/dm2, the growth rate of oxide layers increased by more than 3.5 times, from 0.423 to 1.493 μm/min, respectively. SEM images are characterized by a reduction in the ratio of agglomerate-bumps-region/flatten-region as applied CD increases. However, cracks and larger pores appear when the applied CD is higher than 10.0 A/dm2. X-ray diffraction pattern shows that the main phases of Al, g-Al2O3, α-Al2O3, and W are contained in all coatings. PEO coated sample has the highest hardness of 1290 HV and highest polarization resistance of 8.80 ´ 106 Wcm2 obtained at applied CD 10 A/dm2 which shows the best performance of the coating. The variation in coating performance is explained by microstructure details, specifically phases, compositions of oxide-layers, and micro-pores and cracks.

scholarly journals Wear and Corrosion Resistance of Plasma Electrolytic Oxidation Coatings on 6061 Al Alloy in Electrolytes with Aluminate and Phosphate

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4037
Author(s):  
Zhenjun Peng ◽  
Hui Xu ◽  
Siqin Liu ◽  
Yuming Qi ◽  
Jun Liang
Keyword(s):  
Corrosion Resistance ◽  
Plasma Electrolytic Oxidation ◽  
Salt Spray ◽  
P Element ◽  
Alumina Coating ◽  
Al Alloy ◽  
Wear Properties ◽  
Electrolytic Oxidation ◽  
Plasma Electrolytic ◽  
Peo Coatings

Phosphate and aluminate electrolytes were used to prepare plasma electrolytic oxidation (PEO) coatings on 6061 aluminum alloy. The surface and cross-section microstructure, element distribution, and phase composition of the PEO coatings were characterized by SEM, EDS, XPS, and XRD. The friction and wear properties were evaluated by pin-on-disk sliding tests under dry conditions. The corrosion resistance of PEO coatings was investigated by electrochemical corrosion and salt spray tests in acidic environments. It was found that the PEO coatings prepared from both phosphate and aluminate electrolytes were mainly composed of α-Al2O3 and γ-Al2O3. The results demonstrate that a bi-layer coating is formed in the phosphate electrolyte, and a single-layered dense alumina coating with a hardness of 1300 HV is realizable in the aluminate electrolyte. The aluminate PEO coating had a lower wear rate than the phosphate PEO coating. However, the phosphate PEO coating showed a better corrosion resistance in acidic environment, which is mainly attributed to the presence of an amorphous P element at the substrate/coating interface.

INCORPORATION OF MULTI-WALLED CARBON NANOTUBES INTO OXIDE LAYER FORMED ON AL ALLOY BY PLASMA ELECTROLYTIC OXIDATION

2020 ◽  
Vol 27 (11) ◽  
pp. 2050007
Author(s):  
KOANGYONG HYUN ◽  
JUNG-HYUNG LEE ◽  
SEONG-JONG KIM
Keyword(s):  
Carbon Nanotubes ◽  
Oxide Layer ◽  
Plasma Electrolytic Oxidation ◽  
Aqueous Suspension ◽  
Al Alloy ◽  
Time Curve ◽  
Oxide Layers ◽  
X Ray ◽  
Electrolytic Oxidation ◽  
Plasma Electrolytic

Plasma electrolytic oxidation (PEO) is an electrochemical-based surface modification technique that produces oxide layers on valve metals. The PEO process is performed in an electrolyte solution, which offers the possibility of particles’ incorporation into the growing oxide layer. In this study, we employed a PEO technique on a commercial Al alloy in an aqueous suspension of carbon nanotubes (CNTs) to fabricate CNT-incorporated oxide layer. The voltage–time response was recorded during the process. The surface of the resulting oxide layer was characterized by means of a scanning electron microscope (SEM), an energy-dispersive X-ray spectrometer (EDS), and X-ray diffraction (XRD). It was found from the SEM observation that the CNTs were successfully incorporated into the oxide layer. The PEO with the addition of CNTs led to a delay in time to breakdown (50[Formula: see text][Formula: see text][Formula: see text]s) and a decrease in breakdown voltage (442[Formula: see text][Formula: see text][Formula: see text]V) in the voltage–time curve. The microstructural feature was clearly distinguishable between the oxide layers produced with and without CNTs: a pancake-like structure for PEO without CNTs, and a doughnut-like structure for PEO with CNTs. However, neither the results of the structure analysis nor the elemental analysis provides a clear indication of carbon, even though the presence of CNTs in the oxide layer is evident, suggesting that further optimization of CNT concentration is required.

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