• Journal of the Korean institute of surface engineering
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• v.52 no.4
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• pp.203-210
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• 2019

In this work, anodizing behavior of 6xxx series aluminum alloys was studied under constant current density and constant voltage conditions in 20% sulfuric acid solution by V-t curves, I-t curves, thickness measurement, observations of surface appearance and cross-sectional observation of anodizing films. The film growth rate of the anodizing films on Al6063, Al6061 and Al6082 obtained at 20 V were $0.63{\mu}m/min$. $0.46{\mu}m/min$ and $0.38{\mu}m/min$, respectively. Time to the initiation of imperfections at the oxide/substrate interface under constant current condition was shortened and colors of anodizing films became darker with the amount of alloying elements in 6xxx series aluminum alloys. Based upon the experimental results obtained in this work, it is concluded that maximum anodizing film thickness without interfacial defects is reduced with increasing amount of alloying elements and brighter anodizing films can be obtained by decreasing amount of alloying elements in the aluminum alloys.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.1
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• pp.90-94
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• 2012

This study evaluates the strength of surface treatment parts using the hard anodizing method to the aluminum alloy brake disks. In order to achieve weight reduction of vehicles, Eco-friendly cars parts of the high-quality and competitive price is to equip. Especially while pursuing parts of weight reduction, it has to maintain the strength of the surface of the brake by nature. To enhance surface strength of aluminum alloy, we use hard anodizing technology in the surface treatment. This study is resulted of 3 times greater the hardness value of the hard anodized specimen than the aluminum alloy specimen for the lightweight parts of EV brake disk

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.8
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• pp.87-92
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• 2022

The Al3003 aluminum plate was cut by grinding, milling, sawing, and shearing, and the hard-anodizing surface of the material was investigated. Large burrs were formed during grinding and milling. The brittle anodized film split and migrated along the deformed aluminum surface. During shearing, the hard-anodized film on the blade entry surface cracks and slides along the deforming aluminum. The cutting heat increased the ductility of the aluminum and further promoted burr formation. The oil-based coolant suppressed burrs and prevented chips from sticking to the endmill. It is better to avoid the high cutting speed and slow material feed rate conditions, which increase the cutting temperature and burr in the band saw.

• Corrosion Science and Technology
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• v.22 no.4
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• pp.221-231
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• 2023

Interest in aluminum alloys for the hydrogen valves of fuel cell electric vehicles (FCEVs) is growing due to the reduction in fuel efficiency by the high weight. However, when an aluminum alloy is used, deterioration in mechanical characteristics caused by hydrogen embrittlement and wear is regarded as a problem. In this investigation, the aluminum alloy used to prevent hydrogen embrittlement was subjected to surface treatments by performing hard anodizing and plasma ion nitriding processes. The hard anodized Al alloy exhibited brittleness in which the mechanical characteristics rapidly deteriorated due to porosity and defects of surface, resulting in a decrease in the ultimate tensile strength and modulus of toughness by 15.58 and 42.51%, respectively, as the hydrogen charging time increased from 0 to 96 hours. In contrast, no distinct nitriding layer in the plasma ion-nitrided Al alloy was observed due to oxide film formation and processing conditions. However, compared to 0 and 96 hours of hydrogen charging time, the ultimate tensile strength and modulus of toughness decreased by 7.54 and 13.32%, respectively, presenting excellent resistance to hydrogen embrittlement.

• Journal of the Korean institute of surface engineering
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• v.55 no.6
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• pp.417-424
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• 2022

This research develops an easy-to-use, environmentally friendly method for fabricating functional 1050 aluminum alloy surfaces with excellent corrosion resistance. Functional aluminum surfaces with various nanostructures are fabricated by controlling the experimental conditions of anodizing process. The experiment used a multi-step anodizing process that alternates between two different anodizing modes, mild anodizing (MA) and hard anodizing (HA), together with a pore-widening (PW) process. Among them, the nanostructured surface with a small solid fraction shows superhydrophobicity with a contact angle of more than 170° after water-repellent coating. In addition, the surface with superhydrophobicity is difficult for corrosive substances to penetrate, so the corrosion resistance is greatly improved.

• Journal of the Korean institute of surface engineering
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• v.53 no.5
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• pp.219-226
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• 2020

This paper investigated the characteristics of anodized aluminum 6061-T6 alloy for corrosion and stress corrosion cracking(SCC) under natural seawater. The hard anodizing oxide film formed on the 6061-T6 was a uniform thickness of about 25 ㎛. The corrosion characteristics were performed with a potentiodynamic polarization test. SCC was characterized by a slow strain rate tensile test under 0.005mm/min rate. As a result, the anodizing film showed no significant effect on SCC in the slow strain rate test. However, the corrosion current density of base metal was measured to be approximately 13 times higher than that of the anodized specimen. Therefore, the anodizing film significantly improved the corrosion resistance of 6061-T6 alloy in natural seawater.

• Corrosion Science and Technology
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• v.18 no.6
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• pp.228-231
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• 2019

Aluminum and its alloys have been widely used in various fields because of low weight, high strength, good conductivity, and low price. It is well known that aluminum alloys that cause natural oxide film can inhibit corrosion in wet, salty environments. However, these oxides are so thin that corrosion occurs in a variety of environments. To prevent this problem, an electrochemical anodizing technique was applied to the aluminum alloy surface to form a thick layer of oxide and a unique oxide shape, such as a hierarchical pore structure simultaneously combining large and small pores. The shape of the structures was implemented using stepwise anodization voltages such as 40 V for mild anodizing and 80 V for hard anodizing, respectively. To maximize water repellency, it is crucial to the role of surface structures shape. And a hydrophobic thin film was coated by 1H, 1H, 2H, 2H-Perfluorodecyltrichlorosilane (FDTS) to minimize surface energy of the structure surface. Thus, such nanoengineered superhydrophobic surface exhibited a high water contact angle and excellent corrosion resistance such as low corrosion current density and inhibition efficiency.

• Journal of the Korean institute of surface engineering
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• v.13 no.1
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• pp.8-15
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• 1980

The critical voltage of hard coat range of Al alloys (K 186, 43S) at various electrolytes and the effects of voltage, temperature of electrolytes and concentration of sulfric acid were investigated, m the hope that to find the adequate voltage. Two kind of A1 alloys were anodized in three typical electrolytes and micro vickers hardness of the films were measured. With respect to the relationship between the hardness of the film and the voltage The result of this experiment are as fallows. 1. The critical voltage of hard coat rangs for the electrolytes $H_2SO_4\;10%,\;H_2SO_4\;10%\;+\;H_2C_2O_4\;2H_2O\;10g/l,\;H_2SO_4\;10%\;+\;NaHSO_4\;5%$ was 20V 22V 24V respectively. 2. $H_2SO_4\;10%\;+\;NaHSO_4$ 5% electrolyte was most adventageous among the three electrolyte in the respect of hardness. 3. The effect of concentration of sulphuric acid was not appeared.

• Journal of the Korea Convergence Society
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• v.7 no.5
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• pp.169-173
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• 2016

Anodic oxidation of aluminum has a sulfuric acid method and a oxalic acid method. Sulfuric acid concentration of the sulfuric acid method is 15~20 wt%. In the case of soft anodizing used in the $20{\sim}30^{\circ}C$ range, and voltage is the most used within a DC voltage 13~15V. In the case of hard anodizing used in the $0{\sim}-5^{\circ}C$ range. An aluminum oxide layer is made using sulfuric acid and oxalic acid. In this study, thermal fatigue of aluminum oxide layer which is made using sulfuric acid and oxalic acid is compared. Crack generating temperature of a sulfuric acid method and a oxalic acid method is $500^{\circ}C$ and $600^{\circ}C$. Thermal fatigue of aluminum oxide layer which is made using oxalic acid is better than thermal fatigue of aluminum oxide layer which is made using sulfuric acid. The characteristic of thermal fatigue can be explained by using thermal expansion coefficient of Al and Al2O3 and manufacturing temperature on Al anodizing. It was made possible through the convergent study to propose the manufacturing method of the anodic oxidation product used at a high temperature.

• Corrosion Science and Technology
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• v.19 no.5
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• pp.259-264
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• 2020

Many studies have been conducted to improve the corrosion resistance and durability of various aluminum alloys through the anodizing technique. It is already used as a unique technique for enhancing the properties of aluminum alloys in various industries. This paper investigated the electrochemical corrosion and stress corrosion cracking characteristics of anodized aluminum 5083-H321 alloy in natural seawater. The corrosion characteristics were assessed by the electrochemical technique and potentiodynamic polarization test. The stress corrosion cracking characteristic was evaluated with a slow strain rate tensile test under 0.005 mm/min rate, which showed that the hard anodizing film had a thickness of about 16.8 ㎛. Although no significant characteristics of stress corrosion cracking were observed in the slow strain rate test, the anodized specimen presented excellent corrosion resistance. The corrosion current density was measured to be approximately 4.2 times lower than that of the base material, and no surface damage was observed in the anodic polarization test.