EFFECT OF GRAPHITE ADDITIVES IN ELECTROLYTES ON CHARACTERISTICS OF MICRO-ARC OXIDATION COATINGS ON 7E04 ALUMINUM ALLOY

2019 ◽  
Vol 26 (04) ◽  
pp. 1850178 ◽  
Author(s):  
PING WANG ◽  
JUN PU ◽  
YOU TAO XIAO ◽  
WEN JUN HU ◽  
TING WU ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Aluminum Alloy ◽  
Phase Composition ◽  
Graphite Powder ◽  
Micro Hardness ◽  
Powder Concentration ◽  
Micro Arc Oxidation ◽  
Surface Morphologies

Micro-arc oxidation coatings were fabricated on 7E04 aluminum alloy substrates by micro-arc oxidation (MAO) in the electrolytes with the graphite addition varying from 0 to 8[Formula: see text]g/L (0, 2, 4, 6, 8[Formula: see text]g/L). The effect of graphite concentration on the surface morphologies, micro-hardness, thickness, phase composition and corrosion resistance of coatings was investigated. With the graphite powder concentration increasing, the oxidation voltage decreased gradually and the thickness of coatings firstly dropped down and then went up. It is found that the size of micro-pores and sintered discs declined with increase of graphite concentration. The XRD results indicated that MAO coatings mainly consisted of [Formula: see text]-Al2O3, [Formula: see text]-Al2O3, SiO2 and a little [Formula: see text]-Al2O3. The corrosion resistance of coatings was improved with the addition of graphite powder. The study reveals that the appropriate graphite powder in the electrolytes is essential to promote the performance of the coatings.

Corrosion Resistance of MAO Coatings on Al-Si Alloys

2020 ◽  
Vol 299 ◽  
pp. 749-754
Author(s):  
N.Yu. Dudareva ◽  
E.I. Ustimova ◽  
R.F. Gallyamova
Keyword(s):  
Corrosion Resistance ◽  
Aluminum Alloy ◽  
Design Theory ◽  
Alkaline Electrolyte ◽  
Processing Unit ◽  
Micro Hardness ◽  
Corrosive Solution ◽  
Micro Arc Oxidation ◽  
Study Methodology ◽  
Process Factors

The paper presents the results of an experimental study of the influence of micro-arc oxidation (MAO) on the parameters and the corrosion resistance of MAO-treated surfaces on a high-silicon aluminum alloy, M244 (Si ~ 25 %). The article describes the study methodology, comprising forming a coating on the surface of laboratory samples by means of MAO at different process modes and the study of their parameters, properties, and corrosion resistance. The experiments were conducted in accordance with the 23 full factorial experiment design theory. The MAO process was carried out using a silicate-alkaline electrolyte. MAO factors were as follows: the concentration of the electrolyte components (potassium hydroxide – KOH and liquid glass – Na2SiO3) and electrical parameters of the process, determined by the capacitor capacitance of the processing unit. The samples were tested to define thickness, porosity and micro-hardness of the MAO layer. Being corroded in a corrosive solution for 144 hours, their corrosion resistance was estimated by a mass corrosion rate. The data obtained made it possible to form mathematical models, based on the dependence of corrosion resistance, thickness, porosity and micro-hardness on the process factors. A verification of the obtained models was carried out to determine adequacy and their analysis. Conclusions on the extent of the MAO effect on the corrosion resistance of the samples were drawn. MAO modes were stated to have a significant impact on the corrosion resistance of the samples. MAO should be carried out using low electrolyte concentrations and a low-capacity processing unit for improved corrosion-protective properties of the coating on the M244 (Mahle) aluminum alloy. It is necessary to increase the concentration of the electrolyte components and the processing unit capacity, to obtain a thicker coating with low micro-hardness and porosity.

scholarly journals Effect of Heat Treatment and Sulfuric Acid Anodization on Corrosion Resistance of Aluminum Alloy (AA7075)

2021 ◽  
Vol 40 (1) ◽  
pp. 56-62
Author(s):  
M. Abdullahi ◽  
L.S. Kuburi ◽  
P.T. Zubairu ◽  
U. Jabo ◽  
A.A. Yahaya ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Corrosion Resistance ◽  
Aluminum Alloy ◽  
Sulfuric Acid ◽  
Corrosion Rate ◽  
Polarization Resistance ◽  
Testing Machine ◽  
Palm Kernel ◽  
Engine Oil ◽  
Micro Hardness

This paper, studied the effect of heat treatment and anodization on corrosion resistance of aluminum alloy 7075 (AA7075), with a view to improving its corrosion resistance. Microstructure and micro hardness of the anodic film of the samples were studied with the aid of optical metallurgical microscope and automated micro hardness testing machine. Linear polarization methods were used to assess the corrosion behaviour of the alloy in 0.5M HCl. The microstructure of the annealed sample showed formation of dendrites while precipitation hardened samples in palm kernel oil and SAE 40 engine oil showed precipitates of MgZn2. The SEMS result showed pores and micro cracks on the surfaces of the anodized samples, with the as cast and anodized sample in sulfuric acid exhibiting most compact with few pores. The as cast and sulfuric acid anodized sample shows highest micro hardness value of 205.33 HV, while the least value of 150.67 HV was recorded in sample precipitation hardened in SAE 40 engine oil and anodized in sulfuric acid. Analysis of the potentiodynamic polarization data and curves showed a linear relationship (decrease in icorr, decreases the corrosion rate) between current density and the corrosion rate in all the samples. Higher polarization resistance of 15.093 Ω/cm2 was recorded by the as cast and Sulfuric acid (SA) anodized sample while the precipitation treated in SAE 40 engine oil plus SA anodized sample recorded lowest polarization resistance of 5.2311 Ω/cm2. Heat treatment alone improves corrosion resistance of AA 7075 in 0.5 M HCl solution but heat treatment plus SA anodization does not improve corrosion resistance in the same environment.

A Study of Micro-Arc Oxidation Coatings on Aluminum Alloy Drill Pipe for Offshore Platform

2017 ◽  
Vol 51 (3) ◽  
pp. 16-22 ◽  
Author(s):  
Yan Shen ◽  
Prasanta K. Sahoo ◽  
Yipeng Pan
Keyword(s):  
Corrosion Resistance ◽  
Aluminum Alloy ◽  
Experimental Work ◽  
Structural Characteristics ◽  
Drill Pipe ◽  
Offshore Platform ◽  
Cathode Voltage ◽  
Micro Arc Oxidation ◽  
Anticorrosion Performance

AbstractIn order to enhance the corrosion resistance of a drill pipe for an offshore platform, micro-arc oxidation (MAO) coatings were deposited on the surface of an aluminum alloy drill pipe by MAO technology. The microstructure and anticorrosion performance of the MAO coatings were investigated experimentally. This paper mainly focuses on the experimental work to determine the influence of cathode voltage on the structural characteristics and corrosion resistance of MAO coatings. The results show that the cathode voltage has a significant effect on the preparation of MAO coating during the process. The surface of the coating becomes more compact and smooth with the increase of the cathode voltage. Furthermore, the anticorrosion performance of MAO coatings can effectively be improved with the increase of cathode voltage.

Study on Preparation and the Characteristics of Environment-Friendly Ce-Ti-Mn Conversion Coating on Aluminum Alloy 6061

2014 ◽  
Vol 881-883 ◽  
pp. 1385-1390
Author(s):  
Xian Fang Yang ◽  
Tian Quan Liang ◽  
Wei Wei ◽  
Dong Hui Deng ◽  
Guang Qiao Xu ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Aluminum Alloy ◽  
Room Temperature ◽  
Ph Value ◽  
Conversion Coating ◽  
Environment Friendly ◽  
Aluminum Alloy 6061 ◽  
Coating Characteristics ◽  
Surface Morphologies ◽  
Alloy 6061

Preparation and the characteristics of environment-friendly Ce-Ti-Mn conversion coating on aluminum alloy 6061 were investigated by XRD, FESEM, EDS, TEM and AFM in this paper. It is indicated that coating characteristics such as the surface morphologies, microstructure and corrosion resistance, are greatly influenced by the formation technology at room temperature. The constituents and their concentration, and pH value of the conversion solution have an important role on the feature of Ce-Ti-Mn conversion film, which will significantly influence on the continuity, compactness and the crystalline structure of particles of the film. The concentrations of the main salt K2TiF6and oxidizer KMnO4have significant effect on the characteristics of the conversion coating. The Ce-Ti-Mn film grows in a lamellar way, composing of oxide and/ or hydroxide phases of Ce, Ti and Mn, some of which are amorphous. The formation mechanism of the Ce-Ti-Mn conversion coating is discussed in detail.

EFFECTS OF α-Al2O3 NANOADDITIVE ON THE PROPERTIES OF CERAMIC COATINGS PREPARED IN BORATE ELECTROLYTE BY MICRO-ARC OXIDATION

2012 ◽  
Vol 19 (04) ◽  
pp. 1250038 ◽  
Author(s):  
H. X. LI ◽  
H. H. ZHU ◽  
X. WU ◽  
Z. G. JI
Keyword(s):  
Phase Composition ◽  
Great Influence ◽  
Ceramic Coatings ◽  
Micro Hardness ◽  
X Ray Diffraction ◽  
Micro Arc Oxidation ◽  
Edx Analyses ◽  
6063 Aluminum Alloy ◽  
Α Al2o3 ◽  
Wear Tests

Ceramic coatings have been synthesized on 6063 aluminum alloy by micro-arc oxidation (MAO) technique in the solution of Na2B4O7 electrolyte with and without α- Al2O3 nanoadditive. Effects of α- Al2O3 nanoadditive on the phase composition, micro-structure, micro-hardness, adhesion and wear resistance of the prepared ceramic coatings have been investigated in this paper. The phase composition and microstructure of the MAO coatings were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDX) analyses, respectively. Micro-hardness, adhesion and tribological and wear tests were also performed. The results showed that the α- Al2O3 nanoadditive doped in the electrolyte had great influence on the structural and mechanical properties of the ceramic coatings.

The Research of Micro Arc Oxidation Behavior of the Magnesium Alloy

2013 ◽  
Vol 803 ◽  
pp. 191-195
Author(s):  
Yun Long Zhang ◽  
Mu Qin Li ◽  
Yu Min Zhang ◽  
Ming Hu
Keyword(s):  
Corrosion Resistance ◽  
Phase Composition ◽  
Magnesium Alloy ◽  
Surface Morphology ◽  
Electrolyte Solution ◽  
Oxidation Behavior ◽  
Corrosion Current ◽  
Positive Potential ◽  
Micro Arc Oxidation ◽  
Oxidation Technology

The ceramics coating hadobtained by the micro arc oxidation technology in order to resolve thecorrosion resistance of the Mg alloy.The phase composition, surface morphology,gained weight and polarization behavior of the micro arc oxidation coating wasinvestigated in details. After the introduce of the sodiumcitrate in the electrolyte solution, thespecimen had high relatively positive potential and low corrosion current, sodoped sodium citratewould improve the corrosion resistance properties of the Mg alloy .

Effect of Thermal Oxidation Temperature on the Properties of Micro-Arc Oxidation Ceramic Coating on TC4 Alloy

2016 ◽  
Vol 697 ◽  
pp. 623-626
Author(s):  
Er Xin Ni ◽  
Ji Kang Yan ◽  
Yun Feng Wu ◽  
Yuan Teng ◽  
Zhi Cao Duan ◽  
...  
Keyword(s):  
Phase Composition ◽  
Surface Morphology ◽  
Thermal Oxidation ◽  
Ceramic Coating ◽  
Oxidation Temperature ◽  
Micro Hardness ◽  
Hardness Tester ◽  
Coating Surface ◽  
Tc4 Alloy ◽  
Micro Arc Oxidation

The effect of thermal oxidation temperature on the properties of MAO ceramic coating was investigated, The phase composition and surface morphology of composite oxidation coating were analyzed by XRD and SEM. The micro-hardness of composite oxidation coating were tested by micro hardness tester. The results shown that the composite oxidation coating consists of rutile, anatase Ti and HA. With the thermal oxidation temperature increasing, the micro-hardness of composite oxidation coatings were improved, but when the thermal oxidation temperature rose from 600 °C to 700 °C, the micro-hardness of coating dropped from 575 HV to 505 HV. With the thermal oxidation temperature increasing, the numbers of micro-porous on coating surface was decreased , and the composite oxidation coating became more density.

Effects of graphene on the microstructure and properties of MAO coatings formed on AA7050

2020 ◽  
Vol 111 (6) ◽  
pp. 463-468
Author(s):  
Bo Xu ◽  
Yafeng He ◽  
Xiangzhi Wang ◽  
Weimin Gan
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Corrosion Resistance ◽  
Aluminum Alloy ◽  
Composite Coatings ◽  
Ceramic Coatings ◽  
X Ray Diffraction ◽  
X Ray ◽  
Micro Arc Oxidation ◽  
Scanning Electron

Abstract Ceramic coatings were prepared on the surface of 7050 highstrength aluminum alloy using micro-arc oxidation in an aluminate electrolyte with added graphene. To analyze the surface morphology, roughness, phase composition, and corrosion resistance, scanning electron microscopy, X-ray diffraction, X-ray photoelectron, and electrochemical measurements were used, respectively. The addition of 9 g · L-1 of graphene to the electrolyte decreased the micro-pore size of the composite coatings and improved the density. In addition, with the addition of graphene, the roughness was the lowest, and the corrosion resistance was significantly improved.

Influence of Na2SiO3 Concentration on the Corrosion Behavior of TC4 Ceramic Coatings

2014 ◽  
Vol 971-973 ◽  
pp. 85-88
Author(s):  
Yun Long Zhang ◽  
Cheng Hai Li ◽  
Ming Hu ◽  
Yu Min Zhang
Keyword(s):  
Corrosion Resistance ◽  
Phase Composition ◽  
Sodium Silicate ◽  
Sodium Silicate Solution ◽  
Silicate Solution ◽  
Ceramic Coatings ◽  
Coating Properties ◽  
Silicate Content ◽  
Micro Arc Oxidation ◽  
Oxidation Technology

The micro-arc oxidation technology were utilized to fabricated the ceramics coating in order to improve the corrosion resistance of Ti–6Al–4V alloy (TC4). The sodium silicate solution was introduced into the electrolyte solution for increasing the coating properties. The effect of the sodium silicate content on the phase composition, surface morphology and potentiodynamic polarization behavior was investigated. The results showed that the increase of Na2SiO3 concertration was benefit to improve corrosion resistance of the MAO coating of TC4 alloy. Key words: Micro-arc oxidation, Ceramic Coatings, Corrosion Resistance.

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