scholarly journals FEATURES OF THE FORMATION OF THE COATING STRUCTURE ON TITANIUM-BASED ALLOYS

2021 ◽  
pp. 3-8
Keyword(s):  
Current Density ◽  
Processing Time ◽  
Practical Interest ◽  
Zirconium Sulfate ◽  
Duration Of Treatment ◽  
Protective Properties ◽  
Composition And Structure ◽  
Electrolytic Oxidation ◽  
Plasma Electrolytic ◽  
Galvanostatic Conditions

Previously shown that coatings formed on titanium by plasma electrolytic oxidation (PEO) in an electrolyte with zirconium sulfate Zr(SO4)2 consisted of ZrO2 and TiO2 oxides, their surface layer is enriched with zirconium, they have good protective properties in chlorine-containing media. The resulting layers have a fairly regular distribution of relatively small pores, with a diameter of about 1 μm or less, on the surface. The composition and structure of PEO layers depend on both the composition of the electrolyte and the modes of formation. It is of scientific and practical interest to elucidate the effect of the conditions for the formation of coatings with ZrO2 on titanium and its alloys on their anticorrosive properties in chlorine-containing media. Samples for research were formed under anodic (unipolar) conditions at the same current density and different formation times. The samples were formed in modes with current density 0.08 A/cm2 and processing time (minutes) − 8.5; 9.5; 10; 11; 12; 13; 14; 15; 20; 30; 40; 60. The duration of treatment was chosen as to maximally repeat the anticorrosive characteristics obtained in the previous case. The work uses modern research methods, including electron microscopy, presents the results of further study of ZrO2 + TiO2 / Ti systems formed in an electrolyte with zirconium sulfate Zr(SO4)2. It has been established that coatings are formed on titanium and its alloys in an electrolyte with zirconium sulfate under galvanostatic conditions of the PEO process at i = 0.08 A / cm2 during a processing time of 11-15 min. There is a correlation between the stages of galvanostatic formation of coatings and their anticorrosive properties.

Inhibitor-Containing Composite Coatings on Mg Alloys: Corrosion Mechanism and Self-Healing Protection

2015 ◽  
Vol 245 ◽  
pp. 89-96 ◽  
Author(s):  
Andrey S. Gnedenkov ◽  
Sergey L. Sinebryukhov ◽  
Dmitry V. Mashtalyar ◽  
Sergey V. Gnedenkov
Keyword(s):  
Plasma Electrolytic Oxidation ◽  
Composite Coatings ◽  
Healing Process ◽  
Corrosion Mechanism ◽  
Self Healing ◽  
Protective Properties ◽  
Oxidation Method ◽  
Electrolytic Oxidation ◽  
Plasma Electrolytic ◽  
Electrode Technique

The way of self-healing coating formation at the surface of magnesium alloys by means of plasma electrolytic oxidation method (PEO) with subsequent filling of the obtained layer with inhibitor has been suggested. The electrochemical properties of such coatings have been described in details. The obtained experimental results indicate that the protective properties of the samples with inhibitor-containing coating were increased (IC = 8.6×10–8 A/cm2) in comparison with the samples without coating (5.3×10–5 A/cm2) and the base coating obtained by plasma electrolytic oxidation method (PEO) (3.4×10–7 A/cm2). The local scanning electrochemical methods of surface investigation, notably Scanning Vibrating Electrode Technique (SVET) and Scanning Ion-Selective Electrode Technique (SIET) were used for determining the kinetics and mechanism of the self-healing process. The treatment by the solution containing 8-hydroxyquinoline, which inhibits the corrosion process, enables one to increase the protective properties of the composite coating in 30 times in the corrosion-active environment in comparison with the base PEO-coating and avert the intensive destruction of the material.

scholarly journals Influence of electric current characteristics of the formation process on the properties of PEO-coatings, obtained on MA8 magnesium alloy in potentiodynamic mode

2020 ◽  
pp. 116-123
Author(s):  
С.Н. СУЧКОВ
Keyword(s):  
Magnesium Alloy ◽  
Current Density ◽  
Barrier Properties ◽  
Morphological Properties ◽  
Protective Properties ◽  
Voltage Change ◽  
Coating Formation ◽  
Current Characteristics ◽  
Plasma Electrolytic ◽  
Peo Coatings

Установлено, что в потенциодинамическом режиме формирования покрытий методом плазменного электролитического оксидирования (ПЭО) электрохимические и морфологические свойства получаемых поверхностей можно регулировать, используя максимальную плотность тока. Получены зависимости данной величины от таких параметров, как максимальное значение и скорость изменения напряжения, а также от размеров оксидируемого изделия. Исследована зависимость защитных свойств ПЭО-покрытий, получаемых на магниевом сплаве МА8, от максимальной плотности тока формирования. Проведены морфологические и электрохимические исследования полученных гетерооксидных слоев с целью выявления корреляции свойств покрытий с плотностью тока формирования. Методами сканирующей электронной микроскопии и потенциодинамической поляризации изучены основные защитные свойства ПЭО-покрытий. Результаты свидетельствуют об увеличении толщины и пористости покрытий при росте значений плотности тока формирования. Показано, что при переходе от низких (2 мА/мм2) к высоким (до 12 мА/мм2) максимальным значениям плотности тока поляризационное сопротивление имеет максимум в области значения 4 мА/мм2, что свидетельствует об оптимальном режиме формирования ПЭО-покрытий с высокими барьерными свойствами. It is established that in the potentiodynamic coating-formation mode by plasma electrolytic oxidation (PEO), the electrochemical and morphological properties of the resulting surfaces can be adjusted using the maximum current density. In this paper, the dependences of this value on such parameters as the maximum value and the rate of voltage change, as well as on the size of the oxidized product are obtained. The dependence of the protective properties of PEO-coatings obtained on magnesium alloy MA8 on the maximum density of the formation current is studied. Morphological and electrochemical studies of the obtained heteroxide layers were performed in order to identify the correlation of the coating properties with the density of the formation current. The main protective properties of PEO-coatings have been studied using scanning electron microscopy and potentiodynamic polarization. The results obtained indicate an increase in the thickness and porosity of coatings with an increase in the values of density of the formation current. It is shown that during the transition from low (2 mA/mm2) to high (up to 12 mA/mm2) maximum values of the current density, the polarization resistance has a maximum in range of 4 mA/mm2, which indicates the optimal mode of formation of PEO coatings with high barrier properties.

Formation of Protective Coatings on AMg3 Aluminum Alloy Using Fluoropolymer Nanopowder

2020 ◽  
Vol 312 ◽  
pp. 330-334
Author(s):  
Valeriia S. Filonina ◽  
Konstantine V. Nadaraia ◽  
Dmitry V. Mashtalyar ◽  
Andrey S. Gnedenkov ◽  
Igor M. Imshinetsky ◽  
...  
Keyword(s):  
Aluminum Alloy ◽  
Isopropyl Alcohol ◽  
Protective Coatings ◽  
Composite Coatings ◽  
Protective Properties ◽  
Composite Layers ◽  
Electrolytic Oxidation ◽  
Order Of Magnitude ◽  
Plasma Electrolytic ◽  
Subsequent Modification

The paper presents the results of a study of the protective properties of composite coatings obtained on AMg3 aluminum alloy by plasma electrolytic oxidation (PEO) and subsequent modification of formed oxide layer with superdispersed polytetrafluoroethylene (SPTFE) from a suspension based on isopropyl alcohol. The incorporation of fluoropolymer decreased the porosity of base PEO-coating more than one order of magnitude. Formed composite layers increased wearproof of the samples by more than two orders of magnitude in comparison with PEO-coating. Additionally, polymer-containing coatings has higher adhesion compared to substrate. Formed composite layers possess superhydrophobic properties: contact angle attains 155°.

scholarly journals Formation and Properties of Oxide Coatings with Immobilized Zeolites Obtained by Plasma Electrolytic Oxidation of Aluminum

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1241
Author(s):  
Kristina Mojsilović ◽  
Uroš Lačnjevac ◽  
Srna Stojanović ◽  
Ljiljana Damjanović-Vasilić ◽  
Stevan Stojadinović ◽  
...  
Keyword(s):  
Plasma Electrolytic Oxidation ◽  
Processing Time ◽  
Water Solution ◽  
Activity Levels ◽  
Oxide Coatings ◽  
X Ray ◽  
Electrolytic Oxidation ◽  
Chemical And Phase Compositions ◽  
Plasma Electrolytic ◽  
Peo Coatings

In this paper, we employed plasma electrolytic oxidation (PEO) of aluminum in a water solution of sodium tungstate (Na2WO4∙2H2O) with the addition of the pure and Ce-loaded zeolites clinoptilolite and 13 X for the preparation of oxide coatings. The obtained coatings were characterized with respect to their morphologies and chemical and phase compositions using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, atomic force microscopy, and X-ray diffraction. The prepared coatings contained γ-alumina, WO3, and metallic tungsten. The surface morphologies of the obtained coatings strongly depended on the PEO processing time; the roughness of all coatings increased with PEO time, while porosity decreased with PEO processing time as a result of microdischarge coalescence and growth. All coatings contained elements originating from the substrate and from the electrolytes. Coatings containing zeolites with Ce showed higher photoactivity than those with immobilized pure zeolites. The highest photocatalytic activity levels were observed for coatings containing immobilized Ce-exchanged clinoptilolite processed for 10 min. It was observed that both clinoptilolite and 13X zeolites improved the features of the PEO coatings in a similar manner, making natural and abundant clinoptilolite an excellent candidate for various applications.

The Mechanism of PEO Process on Al–Si Alloys in Zirconate Solution

2012 ◽  
Vol 479-481 ◽  
pp. 178-181
Author(s):  
Ping Wang ◽  
Dao Xin Liu ◽  
Jian Ping Li ◽  
Yong Chun Guo ◽  
Zhong Yang
Keyword(s):  
Growth Rate ◽  
Plasma Electrolytic Oxidation ◽  
Plasma Discharge ◽  
Alkaline Electrolyte ◽  
Zirconia Coating ◽  
Micro Particles ◽  
Composition And Structure ◽  
Electrolytic Oxidation ◽  
Plasma Electrolytic ◽  
Electric Field Force

Zirconia coating was produced on Al-Si alloys by plasma electrolytic oxidation (PEO). The alkaline electrolyte containing Zr(OH)4 powders was used. The composition and structure of the coating were investigated by SEM and XRD. The results show that in the initial stages of oxidation the growth of coating belongs to the stage of anodic oxidation controlled by electrochemical polarization. The growth of coating is mainly outward growth and the growth rate is faster. With elongated treated time and increased thickness of the coating, the growth of coating is mainly ingrowth. In contrast with the stage of anodization, the growth rate of plasma electrolytic oxidation is slower than anodization. The coating consists of t-ZrO2, m-ZrO2, α-Al2O3 and γ-Al2O3.T-ZrO2 is the main phase and distributes in outer layer of the coating, however, α-Al2O3 appears in inner layer of the coating. Many micro-particles appear on the coating surface with dimension of 1-2μm.. In the process of plasma electrolytic oxidation, Zr(OH)4 powders move and deposit on the mouth of plasma discharge channel under the effect of electric field force, then it is transformed to ZrO2 by the high temperature of plasma discharge.

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