Effects of Current Density on the Properties of Microarc Oxidation Coatings Formed on Aluminum Alloy in Silicate-Na2MoO4 Electrolyte

2015 ◽  
Vol 814 ◽  
pp. 398-403 ◽  
Author(s):  
Ping Wang ◽  
Ting Wu ◽  
Xiao Yang Guo ◽  
Ya Peng
Keyword(s):  
Corrosion Resistance ◽  
Aluminum Alloy ◽  
Polarization Curve ◽  
Current Density ◽  
Microarc Oxidation ◽  
Discharge Process ◽  
Micropore Size

Microarc oxidation (MAO) coatings on ZL108 aluminum alloy were prepared in the silicate-Na2MoO4 electrolytes with different current density. The MAO process was studied by measuring the voltage as a function of time. The microstructure, compositions, distribution of element and corrosion resistance of the MAO coatings were investigated by SEM, XRD, EDS, XPS and polarization curve, respectively. With the increasing of current density, the final voltage in the microarc discharge process increased. The results shown that the MAO coatings were mainly composed of mullite, γ-Al2O3, Si, little MoO2 and MoO3. The micropore size, thickness, compositions, distribution of element of the MAO coatings depended on the current density and the amount of MoO2 and MoO3. The corrosion resistance improved as the porosity of the MAO coatings decreasing.

scholarly journals Preparation of Ti–Zr-Based Conversion Coating on 5052 Aluminum Alloy, and Its Corrosion Resistance and Antifouling Performance

Coatings ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 397 ◽  
Author(s):  
Hehong Zhang ◽  
Xiaofeng Zhang ◽  
Xuhui Zhao ◽  
Yuming Tang ◽  
Yu Zuo
Keyword(s):  
Corrosion Resistance ◽  
Surface Modification ◽  
Aluminum Alloy ◽  
Current Density ◽  
Corrosion Current Density ◽  
Salt Water ◽  
Water Immersion ◽  
Chemical Conversion ◽  
Corrosion Current ◽  
Conversion Coating

A chemical conversion coating on 5052 aluminum alloy was prepared by using K2ZrF6 and K2TiF6 as the main salts, KMnO4 as the oxidant and NaF as the accelerant. The surface morphology, structure and composition were analyzed by SEM, EDS, FT–IR and XPS. The corrosion resistance of the conversion coating was studied by salt water immersion and polarization curve analysis. The influence of fluorosilane (FAS-17) surface modification on its antifouling property was also discussed. The results showed that the prepared conversion coating mainly consisted of AlF3·3H2O, Al2O3, MnO2 and TiO2, and exhibited good corrosion resistance. Its corrosion potential in 3.5 wt % NaCl solution was positively shifted about 590 mV and the corrosion current density was dropped from 1.10 to 0.48 μA cm−2. By sealing treatment in NiF2 solution, its corrosion resistance was further improved yielding a corrosion current density drop of 0.04 μA cm−2. By fluorosilane (FAS-17) surface modification, the conversion coating became hydrophobic due to low-surface-energy groups such as CF2 and CF3, and the contact angle reached 136.8°. Moreover, by FAS-17 modification, the corrosion resistance was enhanced significantly and its corrosion rate decreased by about 25 times.

scholarly journals Low Temperature Sealing of Anodized Aluminum Alloy for Enhancing Corrosion Resistance

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4904
Author(s):  
Hyunbin Jo ◽  
Soomin Lee ◽  
Donghyun Kim ◽  
Junghoon Lee
Keyword(s):  
Corrosion Resistance ◽  
Aluminum Alloy ◽  
Current Density ◽  
Corrosion Current Density ◽  
Corrosion Current ◽  
Anodic Oxide ◽  
Nickel Acetate ◽  
Anodized Aluminum ◽  
Corrosive Media ◽  
Nickel Fluoride

Sealing as a post treatment of anodized aluminum is required to enhance the corrosion resistance by filling nanopores, which allow the penetration of corrosive media toward the base aluminum. We designed a mixed sealing solution with nickel acetate and ammonium fluoride by modifying traditional nickel fluoride cold sealing. The concentration of mixed sealing solution affected the reaction rate of sealing and corrosion current density of anodized aluminum alloy. The higher concentration of mixed sealing solution improved the sealing rate, which was represented by a decrease of corrosion current density of anodized aluminum alloy. However, a mixed sealing solution with 2/3 concentration of general nickel fluoride sealing solution operated at room temperature showed the lowest corrosion current density compared to traditional methods (e.g., nickel fluoride cold sealing (NFCS) and nickel acetate hot sealing) and other mixed sealing solutions. Moreover, the mixed sealing solution with 2/3 concentration of general NFCS had a lower risk for over sealing, which increases the corrosion current density by excessive dissolution of anodic oxide. Therefore, the mixed sealing solution with optimized conditions designed in this work possibly provides a new method for enhancing the corrosion resistance of anodized aluminum alloys.

HIGH TEMPERATURE STEAM CORROSION OF MICROARC OXIDATION COATINGS ON 6061 ALUMINUM ALLOY AT 300∘C/3 MPa STEAM

2020 ◽  
pp. 2050030
Author(s):  
YAO QU ◽  
CHAOLIN YANG ◽  
XIAOYUE JIN ◽  
JIANCHENG DU ◽  
WENBIN XUE
Keyword(s):  
High Pressure ◽  
Corrosion Resistance ◽  
Aluminum Alloy ◽  
High Temperature ◽  
Microarc Oxidation ◽  
Low Frequency ◽  
6061 Aluminum Alloy ◽  
Fine Needle ◽  
Pressure Steam ◽  
High Temperature Steam

The structural and phase transformation of microarc oxidation (MAO) coatings on 6061 aluminum alloy at 300∘C/3[Formula: see text]MPa steam were evaluated. After 10 days steam corrosion, the weight loss of coated alloys with 15[Formula: see text][Formula: see text]m and 75[Formula: see text][Formula: see text]m thickness was only about 1/10 and 1/50 of weight gain of bare alloy, respectively. The [Formula: see text]-Al2O3 and [Formula: see text]-Al2O3 phases in the MAO coatings were stable at 300∘C/3[Formula: see text]MPa steam, but many fine needle-like or brick-like boehmite crystalline particles also appeared on coating surface. The boehmite had a large influence on the permittivity of coatings at low frequency. The MAO treatment on 6061 aluminum alloy improved its corrosion resistance at high-temperature and high-pressure steam.

Effect of Current Density on the Microstructure and Corrosion Properties of MAO Coatings on Aluminum Alloy Shock Absorber

2018 ◽  
Vol 764 ◽  
pp. 28-38 ◽  
Author(s):  
Yan Shen ◽  
Hong Xiang Wang ◽  
Yi Peng Pan
Keyword(s):  
Corrosion Resistance ◽  
Aluminum Alloy ◽  
Current Density ◽  
Shock Absorber ◽  
Structural Characteristics ◽  
Ceramic Coatings ◽  
Corrosion Performance ◽  
Cathode Voltage ◽  
Corrosion Properties ◽  
Micro Arc Oxidation

In order to improve the corrosion resistance of shock absorber for ships, the alumina ceramic coatings are carried out on the surface of aluminum alloy shock absorber by micro arc oxidation (MAO) technology. The microstructure and anti-corrosion performance of the MAO coatings were investigated experimentally. This paper mainly focuses on the experimental work to determine the effect of current density on the structural characteristics and corrosion resistance of MAO coatings. The results show that the current density has a significant influence on the preparation of MAO coating during the process. The surface of the coating becomes more compact and smooth with the cathode voltage of 7 A.dm-2. Furthermore, the anti-corrosion performance of the MAO coatings can effectively be improved at the current density of 7 A.dm-2.

Effect of Negative Pulse Voltage on the Microstructure and Corrosion Resistance of Microarc Oxidation Film of A356 Aluminum Alloy

2011 ◽  
Vol 675-677 ◽  
pp. 1193-1196 ◽  
Author(s):  
Guang Huai Peng ◽  
Bao Jun Han ◽  
Ling Fang ◽  
Xue Feng Guo ◽  
Xiao Lian Zhang
Keyword(s):  
Corrosion Resistance ◽  
Aluminum Alloy ◽  
Microarc Oxidation ◽  
Film Surface ◽  
Corrosion Current ◽  
Pulse Voltage ◽  
Thickness Gauge ◽  
A356 Aluminum Alloy ◽  
Negative Pulse ◽  
A356 Aluminum

The effect of negative pulse voltage on the microstructure and corrosion resistance of microarc oxidation film of A356 aluminum alloy treated by microarc technique was investigated by SEM, coating thickness gauge and electrochemical workstation etc. The results show the negative pulse voltage greatly influences the microstructure and corrosion resistance of microarc oxidation film by its electrode reaction. The film thickness increases while the size of pore and roughness of the film surface decreases initially and then increases with negative pulse voltage increasing. The microarc oxidation treatment considerably improved corrosion resistance, and the highest corrosion potential was -1.16V, which was 0.38V higher than that of substrate, and the corrosion current was lower than that of substrate about three orders of magnitude.

Study on the Preparation and Property of the Ceramic Film on the LY12 Aluminium Alloy

2011 ◽  
Vol 291-294 ◽  
pp. 223-227
Author(s):  
Xiao Wen Chen ◽  
De Fen Zhang
Keyword(s):  
Thin Film ◽  
Aluminum Alloy ◽  
Aluminium Alloy ◽  
Current Density ◽  
Microarc Oxidation ◽  
Ceramic Film ◽  
Potentiostatic Method ◽  
Ceramic Thin Film ◽  
Micro Arc Oxidation

The ceramic thin film on the surface of LY12 aluminum alloy were prepared by the method of the microarc oxidation. The appearance of film was observed by stereoscopic microscope, the thickness of film was tested used thickness tester and the corrosion resisting property of sample in solution of 3.5% NaCl was measured by potentiostatic method. The results show that the tightness of film is best when used 8A/ dm2for micro-arc oxidation, the hardness is increased with the increase of current density. The corrosion resisting property of ceramic film in solution of 3.5% NaCl used different current density is different, the corrosion resisting property of ceramic film is first increased and then decreased with the increase of current density, the corrosion resisting property of ceramic film prepared with the current density of 8A/ dm2is best.

The Effect of Trace Boron on Corrosion Resistance of the Casted 0.04C-16Cr Ferritic Stainless Steels in H2SO4 Medium

2012 ◽  
Vol 476-478 ◽  
pp. 263-268 ◽  
Author(s):  
Tie Ming Guo ◽  
Ding Cang Zhang ◽  
Chang Song Han ◽  
Zhi Hui ◽  
Li Ming Zhao
Keyword(s):  
Stainless Steel ◽  
Corrosion Resistance ◽  
Polarization Curve ◽  
Current Density ◽  
Stainless Steels ◽  
Intergranular Corrosion ◽  
General Corrosion ◽  
Ferritic Stainless Steels ◽  
Curve Method ◽  
Intergranular Corrosion Resistance

Three groups of 0.04C-16Cr ferritic stainless steels, with boron quality score of 0ppm, 16ppm and 26ppm, were smelted by a vacuum induction furnace. The chemical soak method, the tafel polarization curve method and the anode circular polarization curve method were used to research their general corrosion and intergranular corrosion resistance. The results showed that both general corrosion and intergranular corrosion of the casted 0.04C-16Cr ferritic stainless steels happened in dilute H2SO4 medium. The resuluts of electrochemical and chemical soak indicate that the addition of B improves intergranular corrosion resistance of 0.04C-16Cr stainless steel, moreover, the intergranular corrosion resistance increases with an increasing content of B. The addtion of B makes the general corrosion rate and self-corrosion current density of the 0.04 C-16Cr stainless steel reduced at active dissolution region in dilute sulphuric acid medium, so the general corrosion resistance of the 0.04 C-16Cr stainless steel is improved. The blunt-dimensional current density of the steel with 26ppm B is the lowest and the passivation zone of it is wider, so the stability of passive film and protection capacity of the steel with 26ppm B are the best. The electrochemical characteristics of general corrosion coincided with the results of soak corrosion.

Effects of KMnO4 on microstructure and corrosion resistance of microarc oxidation coatings on 2024 aluminum alloy

2010 ◽  
Vol 17 (2) ◽  
pp. 223-227 ◽  
Author(s):  
Wei Yang ◽  
Bai-ling Jiang ◽  
Hui-ying Shi ◽  
Lin-yun Xian
Keyword(s):  
Corrosion Resistance ◽  
Aluminum Alloy ◽  
Microarc Oxidation ◽  
2024 Aluminum Alloy

scholarly journals Corrosion Behaviors of Microarc Oxidation Coating and Anodic Oxidation on 5083 Aluminum Alloy

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Haiou Sun ◽  
Liangcai Li ◽  
Zhongyi Wang ◽  
Bin Liu ◽  
Meng Wang ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Aluminum Alloy ◽  
Surface Morphology ◽  
Anodic Oxidation ◽  
Immersion Time ◽  
Microarc Oxidation ◽  
Corrosion Process ◽  
Ion Diffusion ◽  
Corrosion Behaviors ◽  
5083 Aluminum Alloy

The microarc oxidation (MAO) coating and anodic oxidation coating were prepared on 5083 aluminum alloy. The surface morphology, elemental composition, and electrochemical behavior of the two coatings were analyzed. The results proved that the corrosion resistance of the MAO coating is superior than that of the anodic oxidation coating. The protective ability of the coating deteriorated gradually with the increase in immersion time. The corrosion process is controlled by ion diffusion throughout the coatings.

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