• Title, Summary, Keyword: Anodizing

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Properties of double-layered anodizing films on Al alloys formed by two consecutive anodizings (알루미늄 합금의 연속식 양극산화법으로 형성시킨 이중 산화막층의 특성)

  • Jeong, Nagyeom;Choi, Jinsub
    • Journal of the Korean institute of surface engineering
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    • v.54 no.1
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    • pp.30-36
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    • 2021
  • In this study, double-layered anodizing films were formed on Al 5052 and Al 6061 alloys consecutively first in sulfuric acid and then in oxalic acid, and hardness, withstand voltage, surface roughness and acid resistance of the anodizing films were compared with single-layered anodizing films in sulfuric acid and oxalic acid electrolytes. Hardness of the double-layered anodizing film decreased with increasing ratio of inner layer to outer layer for both Al 5052 and Al 6061 alloys, suggesting that outer anodizing film formed in sulfuric acid electrolyte is damaged during the second anodizing in oxalic acid electrolyte. Withstand voltage of the double-layered anodizing films increased with increasing the thickness ratio of inner layer to outer layer. Surface roughness of the double-layered anodizing films were comparable with that of single-layered anodizing film formed in sulfuric acid but higher than that of single layer anodizing film formed in oxalic acid electrolyte. In acid resistance test, all of the double-layered and single-layered anodizing films showed good acid resistance more than 3 h without any visible gas evolution, which is attributable to sealing of pores. Based on the experimental results obtained in this work, it is possible to design a double-layered anodizing film with cost-effectiveness and improved physical and electrical properties by combining two consecutive anodizing processes of sulfuric acid anodizing and oxalic acid anodizing methods.

The study of characterization about magnesium alloy eye-glasses case by anodizing and mixed method (anodizing+burning) (Anodizing과 Burning 공정 혼합으로 표면처리 된 마그네슘합금(AZ31) 안경테 표면의 특성 연구)

  • Yu, Jae-Yong;Lim, Jin-Hwan;Yu, Jae-In;Kim, Jin-Hie;Park, Chang-Hun;Kim, Ki-Hong
    • Journal of the Korean Vacuum Society
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    • v.16 no.3
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    • pp.231-234
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    • 2007
  • During the anodizing and burning anodizing process, appreciable amounts of pores were generated on the surface of magnesium (Mg) alloy which deteriorate the quality of the alloy. However, additional burning process subsequent to the anodizing process reduces the density of pores on the surface. We found that additional burning process can increase the quality of Mg alloy. In addition we found that burning process increases homogeneity of the film thickness as well.

Formation Characteristics of Hard Anodizing Films on 6xxx Aluminum Alloys (6xxx계 알루미늄 합금의 경질 아노다이징 피막 형성 특성 연구)

  • Moon, Sanghyuck;Moon, Sungmo;Lim, Sugun
    • 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.

White coloring of anodized aluminum (알루미늄의 White Color 구현을 위한 양극산화처리 기술)

  • Na, Sang-Jo;Lee, Eun-Han;Son, Seon-Mi
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • pp.239-239
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    • 2015
  • 삼성, LG전자 등 다양한 사업부의 White Anodizing구현기술의 Need는 항상 존재하고 있으며, 특히 White와 Black Color의 콤비네이션으로 친환경 이미지 강조 및 핸드폰의 고급화에 필연적인 메탈화로 작년부터 White Anodizing의 수요요청이 쇄도하고 있다. 그러나 현행 공업용 Anodizing 기술(황산법)은 봉공처리 전 착색공정에서 Red, Blue, Black 등 염료분자와 달리 염료 분자가 비교적 큰 White 염료는 Anodizing으로 성장된 다공성피막 내부로 들어가지 못해 국내 Anodizing전문기업 뿐만아니라 일본 기업 및 연구소 등에서도 무수한 시도를 하고 있지만 현재까지는 완벽한 White Anodizing구현기술이 전무한 상태이다. 이에 당사는 알루미늄합금을 White의 안료나 염료가 아닌 알칼리전해액의 Pulse전류인가 PEO(Plasma electrolytic oxidation)처리 공정에 의거 White Anodizing기술을 개발하고자 하였다. 알칼리 전해질에 의한 Anodizing 처리기술로 White와 유사한 색상을 구현하고 있으나, 수요자가 요구하는 White Anodizing으로 제품을 양산하는데 어려움이 있어 기존 Anodizing 처리 대신 Pulse전류인가 PEO처리기술로 White Color를 구현하여 수요요청이 쇄도한 국내외 기업체에 공급하고자 한다. 본 기술은 알카리 전해액을 사용하므로 친환경적이며, 다공성 피막으로 인한 우수한 도장 밀착성, 실링처리에 의한 내식성 향상, PEO 피막의 우수한 경도 및 내마모성 등을 나타내며, 알루미늄뿐만 아니라 마그네슘합금, 티타늄 등에도 공히 적용이 가능하며, White Anodizing의 특화된 기술로 표면처리기술 우위 선점 및 원가절감 등이 가능하다. 당사는 알루미늄 아노다이징 전문 기업으로서 내식성 목적의 연질 아노다이징 처리 및 고내마모성을 목적으로 하는 자동차 부품 및 기계 부품용 경질 아노다이징 처리를 주로 수행하고 있다. 본 발표에서는 당사의 표면처리 기술 및 알루미늄의 아노다이징에 대한 소개를 하고자 한다.

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Effects of Time and Current Density in Anodizing of Mg-Al Alloy in Alkaline Solution (알카리 수용액에서 Mg-Al 합금의 양극산화시 전류밀도와 양극산화 시간의 효과)

  • Jang Seok-Ki;Kim Seong-Jong;Kim Jeong-Il
    • Journal of Advanced Marine Engineering and Technology
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    • v.29 no.1
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    • pp.107-115
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    • 2005
  • The effects on the formation of anodic oxide films on Mg-Al alloy (AZ91) in 1M-NaOH solution was investigated using parameters of current density and time during anodizing The general tendency has been confirmed that the increase of anodizing time improves the corrosion resistance. It is considered that the formation of anodic oxide film was increased by increasing the applied current and the anodizing time to generate active dissolution reaction In anodizing at constant current density. passivity potentials shifted to noble direction with increasing current densities. It was confirmed that oxygen quantify in anodic oxide films increased with anodizing time. The compact films above 4 $mA/cm^2$ were formed with the shape of an island in grooves at early stage and then grew with combination of the islands

Study on Hardness and Corrosion Resistance of Magnesium by Anodizing and Sealing Treatment With Nano-diamond Powder (양극산화와 나노 다이아몬드 분말 봉공처리에 의한 마그네슘의 경도와 부식에 관한 연구)

  • Kang, Soo Young;Lee, Dae Won
    • Journal of Korean Powder Metallurgy Institute
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    • v.21 no.4
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    • pp.260-265
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    • 2014
  • In this study, in order to increase surface ability of hardness and corrosion of magnesium alloy, anodizing and sealing with nano-diamond powder was conducted. A porous oxide layer on the magnesium alloy was successfully made at $85^{\circ}C$ through anodizing. It was found to be significantly more difficult to make a porous oxide layer in the magnesium alloy compared to an aluminum alloy. The oxide layer made below $73^{\circ}C$ by anodizing had no porous layer. The electrolyte used in this study is DOW 17 solution. The surface morphology of the magnesium oxide layer was investigated by a scanning electron microscope. The pores made by anodizing were sealed by water and aqueous nano-diamond powder respectively. The hardness and corrosion resistance of the magnesium alloy was increased by the anodizing and sealing treatment with nano-diamond powder.

The Effects of Anodizing Process Parameters and Oxidation Temperature under Atmospheric Environment on Morphology of the Pure Titanium by Alternating Current Arc-anodizing (순티타늄의 교류 불꽃 양극산화층 미세조직에 미치는 양극산화공정변수 및 대기산화온도의 영향)

  • Yang, Hack-Hui;Park, Chong-Sung
    • Journal of the Korean institute of surface engineering
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    • v.41 no.1
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    • pp.16-22
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    • 2008
  • Anodizing to form oxide layers on the pure titanium was performed in the electrolyte containing 1.5M $H_2SO_4$, 0.2M $H_3PO_4$, and 2.5wt.% $CuSO_4$ using the ac-biased arc anodizing technique. Titanium oxide layers anodized with different applied voltages, voltage-elevating rates, and anodizing times were investigated. In addition, thermal oxidation test under an atmospheric environment for the arc-anodized specimens was carried out. The thickness of oxide layers were not affected by the voltage-elevating rates, but increased slightly with the increase of anodizing times. The thickness of oxide layers were increased with the increase of voltages, and increased remarkably in the condition of 200V. The size and number of the pore observed in the center of the porous cell were decreased with increase of applied voltage. From the result of thermal oxidation test, it revealed that oxide layer formed by arc anodizing more effective to prevent oxidation of pure titanium.

Fabrication and Characteristics of Porous Silicon (다공성 실리콘의 제조 및 특성에 관한 연구)

  • 이철환;조원일;백지흠;박성용;안춘호;유종훈;조병원;윤경석
    • Journal of the Korean institute of surface engineering
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    • v.28 no.3
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    • pp.182-191
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    • 1995
  • A highly porous silicon layer was fabricated by anodizing single crystalline silicon in a dilute solution of hydrofluoric acid. The color of the porous silicon changed from red and blue to yellow gold during the anodizing process. The current-voltage (I-V) curve of the anodizing process showed a typical Schottky diode rectification form. The cell voltage decreased with the increase of HF concentration in the solution at high current range. However, the voltage was independent on HF concentration in the solution at low current range. The pore size was dependant on anodizing condition (HF concentration, current and anodizing time). The pore size and wall width of porous silicon layer were 4~6 and 1~3 nm, respectively. Surface of the porous silicon was covered with silicon compound ($SiH_x$etc.) according to IR spectrum analysis. The peak wavelength and width of photoluminescence (PL) spectrum of porous silicon were 650~850 nm (1.5~1.9 eV) and 250 nm, respectively. The photoluminescence intensity and peak wavelength, and porosity of porous silicon increased with increasing anodizing current and decreased with increasing HF concentration in the anodizing solution.

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Effect of Anodizing and Dyeing Treatments on Coloring of Al-Mg (Al-Mg합금의 컬러에 미치는 양극산화 및 착색처리의 영향)

  • Bae, Sung Hwa;Lee, Hyun Woo;Son, Injoon
    • Journal of the Korean institute of surface engineering
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    • v.52 no.1
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    • pp.30-36
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    • 2019
  • In this study, we investigated the effects of anodizing time, dyeing treatment time, and variations in coloring concentration on the color of an AA5052 alloy processed by dye-treated anodizing. The outward color of the anodized film changed to deep red according to increases in anodizing time, dyeing treatment time, and coloring concentration; accordingly, lightness $L^*$ decreased and saturation $a^*$ and $b^*$ increased. The concentration of the dye and the UV-visible absorbance showed a nearly perfect linear relationship, allowing a quantitative analysis of the absorbed dye. Because the quantity of absorbed dye increased as anodizing time, dyeing treatment time, and coloring concentration increased, the outward color of the anodized film deepened. In addition, from the GD-OES depth profile, we found that the dye was preferentially absorbed on the surface of the porous anodized film.

Formation Behavior of Anodic Oxide Films on Al 6061 Alloy in Sulfuric Acid Solution (황산 용액에서 Al6061 합금의 아노다이징 피막 형성거동)

  • Moon, Sungmo;Jeong, Kihun;Lim, Sugun
    • Journal of the Korean institute of surface engineering
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    • v.51 no.6
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    • pp.393-399
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    • 2018
  • Formation behavior of aluminum anodic oxide (AAO) films on Al6061 alloy was studied in view of thickness, morphology and defects in the anodic films in 20 vol.% sulfuric acid solution at a constant current density of $40mA/cm^2$, using voltage-time curve, observation of anodized specimen colors and surface and cross-sectional morphologies of anodic films with anodization time. With increasing anodizing time, voltage for film formation increased exponentially after about 12 min and its increasing rate decreased after 25 min, followed by a rapid decrease of the voltage after about 28 min. Surface color of anodized specimen became darker with increasing anodizing time up to about 20 min, while it appeared to be brighter with increasing anodizing time after 20 min. The darkened and brightened surfaces with anodizing time are attributed to an increase in thickness of porous anodic oxide film and a chemical damage of the films due to heat generated by increased resistance of the film, respectively. Cross-sectional observation of AAO films revealed the formation of defects of crack shape at the metal/oxide interface after 15 min which prevents the growth of AAO films. Width and length of the crack-like defect increased with anodizing time up to 25 min of anodizing, and finally the outer part of AAO films was partly dissolved or detached after 30 min of anodizing, resulting in non-uniform surface structures of the AAO films.