Protective and Thermophysical Characteristics of Plasma-Electrolytic Coatings on the Ultra-Light Magnesium Alloy

2021 ◽  
pp. 1-15
Author(s):  
Sergey Grigoriev ◽  
Igor Kondratsky ◽  
Boris Krit ◽  
Valery Ludin ◽  
Varvara Medvetskova ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Thermal Diffusivity ◽  
Magnesium Alloys ◽  
Ceramic Coatings ◽  
Specific Electrical Conductivity ◽  
Technological Parameters ◽  
Thermophysical Characteristics ◽  
Light Alloy ◽  
Plasma Electrolytic ◽  
Integral Assessment

Abstract Magnesium alloys are now widely used for various purposes due to their unique properties despite the significant disadvantage associated with low corrosion resistance. The plasma-electrolytic oxidation (PEO), which allows the formation of ceramic coatings on the surface of magnesium alloys, is the most advanced and effective method for their protection. But firstly, PEO process of magnesium alloys has some difficulties, and secondly, PEO coatings affect the thermophysical characteristics of the modified materials, in particular they reduce thermal diffusivity. The presented work is devoted to the development of the technological parameters for formation of protective coating on the ultra-light alloy Mg-8Li-1Al-0.6Ce-0.3Y by the PEO method. The results analyses of electrolytes acidity and specific electrical conductivity before and after PEO process and also investigation data of the coatings structure and surface morphology are presented. An integral assessment of the ability of thermal diffusivity and corrosion resistance of the modified alloy was made. Studying of protective and thermophysical characteristics of the obtained coating showed that it provides a sufficiently high corrosion protection, despite the relatively small thickness, and the presence of pores and slightly (not more than 5%) reduces the thermal diffusivity of the magnesium ultra-light alloy.

The Growth Process of the PEO Films under Escalating Voltage Waveform

2011 ◽  
Vol 239-242 ◽  
pp. 720-723
Author(s):  
Li Wang ◽  
Wen Fu ◽  
Li Chen
Keyword(s):  
Corrosion Resistance ◽  
Growth Process ◽  
Ceramic Coatings ◽  
Voltage Waveform ◽  
Potentiodynamic Polarization Curves ◽  
Initial Stage ◽  
Electrolytic Oxidation ◽  
Superior Corrosion Resistance ◽  
Plasma Electrolytic ◽  
Peo Coatings

In order to get a clear picture for describing the growth process of plasma electrolytic oxidation coatings under escalating voltage waveform, the characteristics of PEO coatings formed at different reaction stages were systemically investigated. The morphology and corrosion resistance of the films were studied by scanning electron microscope and potentiodynamic polarization curves. The uniform, semi-transparent and better corrosion resistance of the oxide films on the magnesium electrode surface were formed owe to the extended anodizing time at the initial stage under escalating voltage mode. After sparking occurred, generated ceramic coatings were brokedown, melted, cooled and solidified continuously, so the ceramic coatings were uniform and dense. It also exhibited superior corrosion resistance.

Effect of Plasma Electrolytic Surface Treatment on the Corrosion Characteristics of the Ti-6Al-4V in Acidic, Industrial and Marine Environments

2012 ◽  
Vol 710 ◽  
pp. 677-682 ◽  
Author(s):  
S. Suresh ◽  
K. Pavankumar ◽  
N. Rameshbabu ◽  
K. Venkateswarlu
Keyword(s):  
Corrosion Resistance ◽  
Surface Treatment ◽  
Coating Thickness ◽  
Potentiodynamic Polarization ◽  
Ceramic Coatings ◽  
Test Results ◽  
Wide Range ◽  
Structural Parts ◽  
Plasma Electrolytic ◽  
Corrosive Environments

Titanium and its alloys find wide range of applications in aerospace, marine and automobile industries due to their excellent properties like high strength to weight ratio and good mechanical behaviour. Accordingly, the structural parts made of these alloys are being exposed to different corrosive environments. Therefore, the electrochemical stability of these structural parts needs to be significantly improved for their extended life time and effective functioning. The objective of the present work is to examine the effect of plasma electrolytic surface treatment in improving the corrosion resistance of Ti-6Al-4V in simulated acidic (0.5M H2SO4), marine (3.5% NaCl) and sulphur containing industrial (0.5M Na2SO4) environments. PEO is a relatively new technique for producing ceramic coatings on light metal alloys by employing higher voltage and current than anodizing. The Ti-6Al-4V was surface treated by plasma electrolytic oxidation (PEO) technique for 12 min under optimized conditions of electrical processing parameters and electrolyte chemistry. The logically selected electrolyte system consisting of 10 g of tri-sodium ortho phosphate (Na3PO4.12H2O), 2 g of sodium meta silicate (Na2SiO3.9H2O) and 2 g of potassium hydroxide (KOH) in 1 L of double distilled water was employed. The decisively optimized electrical parameters were fixed as 75% for the duty cycle, 1500 Hz for the pulse frequency and 0.1 A/cm2 for the current density. The phase composition of the resulted coating was analyzed by the X-ray diffraction (XRD) technique. The coating thickness and the elemental composition of the coating were assessed using a scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS). The corrosion characteristics were determined by potentiodynamic polarization and electrochemical impedance spectroscopic (EIS) measurements. The XRD results demonstrated that the resulted coatings consisted of both anatase and rutile phases. The SEM results showed a coating thickness of about 15 µm and a canal like surface morphology with inter-connected open pores over the coating surface. The potentiodynamic polarization test results, in general, showed a minimum of about two orders of magnitude improvement in the corrosion resistance of the treated Ti-6Al-4V compared to that of the untreated in all the three corrosive environments. The EIS test results exhibit comparatively higher AC impedance and higher bode angle over the entire frequency range indicating an improved corrosion resistance of the surface treated Ti-6Al-4V. Thus the plasma electrolytic surface treatment with optimized process parameters, made the Ti-6Al-4V electrochemically stable by significantly improving its corrosion resistance in all the three environmental conditions.

Corrosion Behavior of Surfaced AM50 Magnesium Alloys under Stress Conditions

2010 ◽  
Vol 95 ◽  
pp. 79-83
Author(s):  
Amir Eliezer
Keyword(s):  
Corrosion Resistance ◽  
Magnesium Alloys ◽  
Open Circuit Potential ◽  
Electrochemical Impedance ◽  
Spinel Phase ◽  
Ceramic Coatings ◽  
Open Circuit ◽  
Stress Conditions ◽  
X Ray Diffraction ◽  
X Ray

Micro-arc oxidization of AM50 magnesium alloys was studied. The influence of micro-arc oxidization process was investigated; phase structure were analyzed using X-ray diffraction (XRD). Open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) were used to evaluate the corrosion resistance of ceramic coatings formed on magnesium alloys under stress conditions. XRD analyses indicate that the ceramic coatings fabricated on the surface of magnesium alloys by micro-arc oxidization are composed of spinel phase MgAl2O4 The corrosion resistance of ceramic coatings is improved compared with magnesium alloy substrate.

Simultaneous Reduction of Wear and Corrosion of Titanium, Magnesium and Zirconium Alloys by Surface Plasma Electrolytic Oxidation Treatment

2008 ◽  
Vol 38 ◽  
pp. 27-35 ◽  
Author(s):  
H.M. Nykyforchyn ◽  
V.S. Agarwala ◽  
M.D. Klapkiv ◽  
V.M. Posuvailo
Keyword(s):  
Corrosion Resistance ◽  
Plasma Electrolytic Oxidation ◽  
Synthesis Method ◽  
Zirconium Alloys ◽  
Ceramic Coatings ◽  
Oxide Ceramic ◽  
Wear And Corrosion ◽  
Electrolytic Oxidation ◽  
Wear And Corrosion Resistance ◽  
Plasma Electrolytic

Titanium, magnesium and zirconium alloys are widely used in industrial applications, which require high wear and corrosion resistance. However current methods of improving these properties often do not satisfy the requirements of service and functional properties. An alternative approach is the application of oxide-ceramic coatings using high temperature process. The coatings are applied by spark discharge plasma in the metal-electrolyte system at high voltages - PEO (plasma electrolytic oxidation) as an oxide synthesis method. This method has shown good results for aluminium alloys and with good prospects to be used for titanium, magnesium and zirconium alloys. Development of PEO technology to improve the wear and corrosion resistance of titanium, magnesium and zirconium alloys is discussed in this paper. It describes the methods for obtaining the required layer-thickness for a specified hardness, porosity, wear and corrosion resistance, sets up the optimal process parameters (voltage/current) by taking the relation of anodic to cathodic currents into account, and establishing the electrolyte content of different dopants.

scholarly journals The effect of electrolysis conditions during microarc oxidation on the phase-structural state, hardness and corrosion resistance of magnesium alloys

2020 ◽  
Vol 21 (3) ◽  
pp. 545-551
Author(s):  
V.V. Subbotina ◽  
V.V. Belozerov
Keyword(s):  
Corrosion Resistance ◽  
Phase Composition ◽  
Magnesium Alloys ◽  
Protective Coatings ◽  
Microarc Oxidation ◽  
High Hardness ◽  
Ceramic Coatings ◽  
Functional Layer ◽  
Different Types ◽  
Spinel Mgal2o4

By the method of microarc oxidation for different types of electrolytes (which include KOH, Na2SiO3, Н2О2, NaOH, NaAlO2, Na5P3O10, NaF) and electrolysis conditions, multifunctional ceramic coatings on a magnesium alloy were obtained. The phase composition of the coating includes magnesium oxide (MgO), spinel MgAl2O4, Mg2SiO4 and Мg3(РО4)2 compounds. The phase composition of the coatings is determined by the composition of the electrolyte. The obtained MAO coatings provide high hardness, which is 1500 to 7300 MPa, as well as high corrosion resistance. The results obtained make it possible to recommend MAO coatings on magnesium alloys both as an external (functional) layer and for the formation of an underlayer for the subsequent application of protective coatings (varnishes, polymers, polytetrafluoroethylene, in particular).

Corrosion Protection of a SiCp/ZL101 Composites by Using Plasma Electrolytic Oxidation Method

2009 ◽  
Vol 79-82 ◽  
pp. 1071-1074
Author(s):  
Shi Hai Cui ◽  
Hong Tao Tang ◽  
Jian Yu Li ◽  
Jian Min Han
Keyword(s):  
Corrosion Resistance ◽  
Plasma Electrolytic Oxidation ◽  
Salt Spray ◽  
Xrd Analysis ◽  
Ceramic Coatings ◽  
Immersion Test ◽  
Aluminum Composites ◽  
Electrolytic Oxidation ◽  
Plasma Electrolytic ◽  
Α Al2o3

A dense ceramic coatings with a thickness of 95μm was fabricated on a SiCp/ZL101 aluminum composites by using a plasma electrolytic oxidation(PEO) method. The XRD analysis showed that the PEO coating was mainly composed of α-Al2O3 γ-Al2O3 and mullite.The corrosion resistance of the PEO coatings and SiCp/ZL101 aluminum composites was estimated by the immersion test, salt spray test and electrochemical test. All the test results showed that the corrosion resistance of the composite was improved by the existence of the ceramic coating.

Electrochemical Characteristics of PEO Treated Electric Arc Coatings on Lightweight Alloys

2010 ◽  
Vol 138 ◽  
pp. 55-62 ◽  
Author(s):  
H.M. Nykyforchyn ◽  
V.I. Pokhmurskii ◽  
M.D. Klapkiv ◽  
Mykhajlo M. Student ◽  
Juliet Ippolito
Keyword(s):  
Corrosion Resistance ◽  
Ceramic Coatings ◽  
Electric Arc ◽  
Arc Spraying ◽  
Oxide Ceramic ◽  
Electrochemical Characteristics ◽  
Ti Alloys ◽  
Oxide Phases ◽  
Oxide Ceramic Coatings ◽  
Plasma Electrolytic

The complex technology of the surface treatment of Al, Mg, Ti alloys for size reconstruction and strengthening is presented herein. This consists of electric arc spraying of aluminum alloys or powder wire in an aluminum shell and then treatment with plasma electrolytic oxidation (PEO). Once treated, oxide-ceramic coatings maintain extreme hardness, durability and resistance to wear. At the same time their corrosion-resistant properties are also significant. Dynamic potential dependences were studied for electric arc Al coatings and PEO treatments on Al, Mg, Ti alloys and corrosion currents were analyzed for exposure to a corrosive environment for a period of from 1 hour to 30 days. It was established that PEO treated coatings on Al alloys have a higher corrosion resistance than untreated sprayed coatings. In Mg alloys, an intermediate layer of aluminum electric arc coating between the substrate and PEO-treated coating is necessary in order to ensure high corrosion resistance. This is due to the specifics of the formation of the MgO and Al2O3 oxide phases in the plasma discharge channels. At the same time Al coatings on Ti alloys, including those of post-PEO treatment, were characterized as having lower corrosion resistance within the range of electrode potential from corrosion potential up to repassivation potential, than were untreated Ti-alloys. Yet it was found that the corrosion resistance of PEO treated coatings increases at higher anode potentials. Under cathode polarization the hydrogen discharge is less likely to occur on PEO-coatings than on untreated Ti alloys which more effectively prevents hydrogenation.

Corrosion Properties of Plasma Electrolytic Oxidation Ceramic Coatings on an A356 Alloy Tested in an Ethanol-Gasoline Fuel (E85) Medium

2011 ◽  
Vol 282-283 ◽  
pp. 774-778
Author(s):  
Zhi Jing Peng ◽  
Ying Chen ◽  
Xue Yuan Nie
Keyword(s):  
Corrosion Resistance ◽  
Plasma Electrolytic Oxidation ◽  
A356 Alloy ◽  
Current Mode ◽  
Ceramic Coatings ◽  
Corrosion Properties ◽  
Cross Sectional ◽  
Electrolytic Oxidation ◽  
Zero Resistance ◽  
Plasma Electrolytic

Ceramic oxide coatings were prepared on an aluminum A356 alloy by a plasma electrolytic oxidation (PEO) technique under unipolar, bipolar and duplex unipolar/bipolar current modes. Cross-sectional morphologies of the coatings were studied using a scanning electron microscope (SEM). The corrosion behavior of the coated and uncoated samples was evaluated in ethanol-gasoline E85 fuels through potentiodynamic polarization and zero resistance ammeter (ZRA) testing methods. The results indicated that all the coatings had a better corrosion resistance compared to the uncoated substrate. The unipolar current mode created the PEO coating with a thicker coating microstructure and thus a better corrosion resistance, compared to a bipolar current mode. The duplex treatments of unipolar/bipolar or bipolar/unipolar current modes produced the best performance of the coatings against galvanic corrosions caused by a steel/Al coupling in the E85 fuel medium.

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