• Corrosion Science and Technology
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• 제21권6호
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• pp.487-494
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• 2022

Anodizing is a typical electrochemical surface treatment method that can improve the corrosion and insulating properties of aluminum alloys. The anodization process can obtain a dense structure. It can be used to artificially grow the thickness of an anodization film. Aluminum 3003 alloy used in this study is the most commonly used alloy for batteries due to its high strength and excellent formability as well as its weldability and corrosion resistance. Aluminum 3003 alloy was anodized at 0 ℃ with 0.3 M oxalic acid at 20 V, 40 V, or 60 V for 1 hour, 6 hours, or 12 hours. As a result of analyzing the composition of each specimen with an Energy Dispersive Spectrometer (EDS), aluminum was converted into an oxide film. The thickness of the formed anodization film increased when the applied voltage and anodization time increased. High corrosion potential values and low corrosion current density values were observed for the thickest oxide layer. The anodization film formed by anodization acted as a protective layer. The electrical resistance increased as the applied voltage and anodization time increased.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2018년도 춘계학술대회 논문집
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• pp.67-67
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• 2018

The 5xxx series aluminum alloys are recently used in not only marine system but also automotive area because of a low density material, good mechanical properties and better resistance to corrosion. However, Aluminum alloys are less resistant than the purest aluminum such as 1xxx aluminum alloy. Electrochemical anodization technique has attracted in the area of surface treatment because of a simple procedure, a low-cost efficiency than other techniques such as lithography and a large volume of productivity, and so on. Here, The relationship between the corrosion behavior and the thickness of aluminum anodic oxide have been studied. Prior to anodization, The 5052 aluminum sheets ($30{\times}20{\times}1mm$) were degreased by ultra-sonication in acetone and ethanol for 10 minutes and eletropolished in a mixture of perchloric acid and ethanol (1:4, volume ratio) under an applied potential of 20V for 60 seconds to obtain a regular surface. During anodization process, Aluminum alloy was used as a working electrode and a platinum was used as a counter electrode. The two electrodes were separated at a distance of 5cm. The applied voltage of anodization is conducted at 40V in a 0.3M oxalic acid solution at $0^{\circ}C$ with appropriate magnetic stirring. The surface morphology and the thickness of AAO films was observed with a Scanning Electron Microscopy (SEM). The corrosion behavior of all samples was evaluated by an open-circuit potential and potentio-dynamic polarization test in 3.5wt% NaCl solution. Thus, The corrosion resistance of 5052 aluminum alloy is improved by the formation of an anodized oxide film as function of increase anodization time which artificially develops on the metal surface. The detailed electrochemical behavior of aluminum 5052 alloy will be discussed in view of the surface structures modified by anodization conditions such as applied voltages, concentration of electrolyte, and temperature of electrolyte.

• 한국자기학회지
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• 제17권2호
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• pp.90-94
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• 2007

유연하고 얇은 0.025 mm와 0.2 mm의 두께를 지닌 알루미늄 포일을 사용하여 다공성 알루미나 막을 제작하였다. 알루미늄 포일들은 에탄올/과염소산 용액에서 전해연마하여 표면처리를 하였으며, 0.3 M의 옥살산 용액 안에서 양극산화 시켰다. 양극산학 시용액의 온도는 $9^{\circ}C$로 유지시켰으며, 전극에 가해주는 전압을 0.4와 40 V 사이에서 변화시킨 후, 형성된 알루미나 막의 표면을 주사전자현미경으로 관찰하였다. 관찰 결과, 장시간의 양극 산화 시 사용되는 전압의 크기가 1 V 이상일 경우 강한 전기분해 반응으로 인해 생성된 산화막 표면이 파괴되어 있음을 확인할 수 있었다. 반면 1 V 이하로 처리할 경우, 장시간에 걸쳐 안정적으로 양극산화시킬 수 있음을 알 수 있었다. 이 실험을 통해 얇은 알루미늄 포일의 경우 두꺼운 알루미늄 판과 달리 장시간의 양극산화를 통해 다공성 알루미나 막을 형성하기 위해선 1 V 이하의 낮은 전압이 요구되는 것을 확인할 수 있었다.

• Corrosion Science and Technology
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• 제21권6호
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• pp.495-502
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• 2022

Anodization is a representative electrochemical surface treatment method that can improve both heat resistance and corrosion resistance by forming an anodization film on the surface of the aluminum. However, these properties can be changed after an additional heat treatment process. In this study, Al 6061 was subjected to an anodization process at 60 V for 1 hour, 5 hours, or 9 hours. An additional heat treatment process was performed at 500 ℃ for 30 minutes. Field emission scanning electron microscopy (FE-SEM) analysis revealed that the thickness of the anodized film was increased in proportion to the anodization time. Both pore size and pore diameter of the anodized film was also increased after anodization. After an additional heat treatment process, there were no significant changes in the thickness, pore size, or pore diameter of the anodized film. Heat resistance was confirmed through thermal analysis and chemical resistance was evaluated with a potentiodynamic polarization test.

• Corrosion Science and Technology
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• 제5권4호
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• pp.137-140
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• 2006

The effect of pre-existing barrier-type film on porous aluminum oxide film formation during anodization was investigated to control the uniform film growth rate. Initial potential fluctuations during anodization indicated that the breakdown of barrier-film is preceded before the porous formation and the induction time for the porous film growth increases with the increases of pre-existing film thickness. The porous film growth mechanism is lot affected by the presence of barrier film on aluminum surface. In parallel, uniform growth of barrier film underneath the porous structure was attained by two-step anodization processes.

• 한국재료학회지
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• 제13권9호
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• pp.593-597
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• 2003

Anodic aluminum oxide (AAO) membrane was made of aluminum sheet (99.6%, 0.2 mm thickness). The regular array of hexagonal nano pores or channels were prepared by two step anodization process. A detail description of the AAO fabrication is presented. After the 1st anodization in oxalic acid (0.3 M) at 45 V, The formed AAO was removed by etching in a solution of 6 wt% $H_3$$PO_4$＋1.8 wt% $H_2$$CrO_4$. The regular arrangement of the pores was obtained by the 2nd anodization, which was carried out in the same condition as the 1st anodization. Subsequently, the alumina barrier layer at the bottom of the channel layer was removed in phosphoric acid (1M) after removing of aluminum. Pore diameter, density, and thickness could be controlled by the anodization process parameters such as applied voltage, anodizing time, pore widening time, etc. The pore diameter is proportional to the applied voltage and pore widening time. The pore density and thickness can be controlled by anodization temperature and voltage.

• Corrosion Science and Technology
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• 제21권6호
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• pp.476-486
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• 2022

Recently, aluminum 6061 instead of copper alloy is used for cooling heat exchangers used in the internal combustion of engines due to its economic feasibility, lightweight, and excellent thermal conductivity. In this study, aluminum 6061 alloy was anodized with oxalic acid, phosphoric acid, or chromic acid as an anodizing electrolyte at the same concentration of 0.3 M. After the third anodization, FDTS, a material with low surface energy, was coated to compare hydrophobic properties and anti-icing characteristics. Aluminum was converted into an anodization film after anodization on the surface, which was confirmed through Energy Dispersive X-ray Spectroscopy (EDS). Pore distance, interpore distance, anodization film thickness, and solid fraction were measured with a Field Emission Scanning Electron Microscope (FESEM). For anti-icing, hydrophobic surfaces were anodized with oxalic acid, phosphoric acid, or chromic acid solution. The sample anodized in oxalic acid had the lowest solid fraction. It had the highest contact angle for water droplets and the lowest contact hysteresis angle. The anti-icing contact angle showed a tendency to decrease for specimens in all solutions.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 춘계학술발표강연 및 논문개요집
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• pp.53-53
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• 2003

There has been increasing interest in the fabrication of nano-sized structures because of their various advantages and applications. Anodic Aluminum Oxide (AAO) is one of the most successful methods to obtain highly ordered nano pores and channels. Also It can be obtained diverse pore diameter, density and depth through the control of anodization condition. The three types of substrates were used for anodization; sheets of Aluminum on Si wafer and Aluminum on Mo-coated Si wafer. In Aluminum sheet, a highly ordered array of nanoholes was formed by the two step anodization in 0.3M oxalic acid solutions at 10$^{\circ}C$ After the anodization, the remained aluminum was removed in a saturated HgCl$_2$ solution. Subsequently, the barrier layer at the pore bottom was opened by chemical etching in phosphoric acid. Finally, we can obtain the through-channel membrane. In these processes, the effect of various parameters such as anodizing voltage, anodizing time, pore widening time and pre-heat treatment are characterized by FE-SEM (HITACH-4700). The pore size. density and growth rate of membrane are depended on the anodizing voltage and temperature respectively. The pore size is proportional to applied voltage and pore widening time The pore density can be controlled by anodizing temperature and voltage.

• Corrosion Science and Technology
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• 제22권6호
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• pp.399-407
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• 2023

This study investigated the formation of oxide films on 6061 aluminum (Al) alloy and their impacts on corrosion resistance efficiency by regulating anodization voltage. Despite advantageous properties inherent to Al alloys, their susceptibility to corrosion remains a significant limitation. Thus, enhancing corrosion resistance through developing protective oxide films on alloy surfaces is paramount. The first anodization was performed for 6 h with an applied voltage of 30, 50, or 70 V on the 6061 Al alloy. The second anodization was performed for 0.5 h by applying 40 V after removing the existing oxide film. Resulting oxide film's shape and roughness were analyzed using field emission-scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). Wettability and corrosion resistance were compared before and after a self-assembled monolayer (SAM) using an FDTS (1H, 1H, 2H, 2H-Perfluorodecyltrichlorosilane) solution. As the first anodization voltage increased, the final oxide film's thickness and pore diameter also increased, resulting in higher surface roughness. Consequently, all samples exhibited superhydrophilic behavior before coating. However, contact angle after coating increased as the first anodization voltage increased. Notably, the sample anodized at 70 V with superhydrophobic characteristics after coating demonstrated the highest corrosion resistance performance.

• 한국산학기술학회논문지
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• 제13권10호
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• pp.4757-4761
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• 2012

알루미늄 기판 및 양극산화 공정을 사용하여 LED Chip on Board(COB) 패키지를 제작하였다. 선택적 양극산화 공정을 적용하여 알루미늄 기판 상에 알루미나를 형성하고 이를 COB 패키지 절연층으로 사용하였으며, 비아홀 내부가 충진된 구조의 Thermal Via를 구현하였다. 패키지 기판 종류에 따른 열저항 및 발광효율 변화를 파악하기 위해 알루미늄 기판과 알루미나 기판을 제작하고 이를 각각 비교 분석하였다. Thermal Via가 적용된 알루미늄 기판이 51%의 열저항 개선 및 14%의 발광효율 향상 특성을 보여주었다. 이러한 결과는 선택적 양극산화 공정 및 Thermal Via 구조적용으로 COB 패키지의 방열 특성이 향상되었음을 의미한다. 또한 동일한 전력 소모시 LED 칩 개수에 따른 COB 패키지의 열저항 및 발광효율 변화를 분석함으로써 다수 칩의 효율적인 배치가 열저항 및 발광효율을 증가시킬 수 있음을 확인하였다.