Mg은 구조용 금속재료 중 무게가 가장 가벼우며, 비강도, 비강성, 주조성, 기계가공성, 충격특성, 진동 흡수능 등이 우수하여 수송기기 뿐만 아니라 전자기기, 스포츠레저, 의료기기, 군수용품, 산업용 기기, 로봇 등 산업 전반에 걸쳐 경량화가 요구되는 분야에 적용되고 있다. 특히 최근에는 자동차 부품에 대해 Mg 소재의 생산 및 사용량이 급증하고 있는 추세이며, 한정된 에너지 자원의 효율적 이용과 환경오염 저감이라는 사회적 요구의 증대로 인하여 차체 경량화를 위한 핵심소재로서 그 중요성이 부각되고 있다. 이에 따라 주요 선진국은 차세대 전략소재로 Mg 소재 산업을 집중 육성하고 있으며, 국내에서도 “녹색성장 5개년 계획”, “신성장동력”, “World Premier ...
Mg은 구조용 금속재료 중 무게가 가장 가벼우며, 비강도, 비강성, 주조성, 기계가공성, 충격특성, 진동 흡수능 등이 우수하여 수송기기 뿐만 아니라 전자기기, 스포츠레저, 의료기기, 군수용품, 산업용 기기, 로봇 등 산업 전반에 걸쳐 경량화가 요구되는 분야에 적용되고 있다. 특히 최근에는 자동차 부품에 대해 Mg 소재의 생산 및 사용량이 급증하고 있는 추세이며, 한정된 에너지 자원의 효율적 이용과 환경오염 저감이라는 사회적 요구의 증대로 인하여 차체 경량화를 위한 핵심소재로서 그 중요성이 부각되고 있다. 이에 따라 주요 선진국은 차세대 전략소재로 Mg 소재 산업을 집중 육성하고 있으며, 국내에서도 “녹색성장 5개년 계획”, “신성장동력”, “World Premier Material(WPM)” 등을 통해 Mg 소재산업을 대표적인 녹색소재로 육성하고 있다. Mg 합금은 상온에서 압연가공이 어려워 폭넓은 어플리케이션(application)에 제약이 많이 있었다. 최근 노트북 컴퓨터, 휴대폰 케이스로 사용이 증가하는 배경에는 가공방법의 큰 진전을 보인 영향이 크다.
Mg은 구조용 금속재료 중 무게가 가장 가벼우며, 비강도, 비강성, 주조성, 기계가공성, 충격특성, 진동 흡수능 등이 우수하여 수송기기 뿐만 아니라 전자기기, 스포츠레저, 의료기기, 군수용품, 산업용 기기, 로봇 등 산업 전반에 걸쳐 경량화가 요구되는 분야에 적용되고 있다. 특히 최근에는 자동차 부품에 대해 Mg 소재의 생산 및 사용량이 급증하고 있는 추세이며, 한정된 에너지 자원의 효율적 이용과 환경오염 저감이라는 사회적 요구의 증대로 인하여 차체 경량화를 위한 핵심소재로서 그 중요성이 부각되고 있다. 이에 따라 주요 선진국은 차세대 전략소재로 Mg 소재 산업을 집중 육성하고 있으며, 국내에서도 “녹색성장 5개년 계획”, “신성장동력”, “World Premier Material(WPM)” 등을 통해 Mg 소재산업을 대표적인 녹색소재로 육성하고 있다. Mg 합금은 상온에서 압연가공이 어려워 폭넓은 어플리케이션(application)에 제약이 많이 있었다. 최근 노트북 컴퓨터, 휴대폰 케이스로 사용이 증가하는 배경에는 가공방법의 큰 진전을 보인 영향이 크다.
Magnesium alloys are commonly utilized as lightweight materials having significantly good physico-chemical properties such as relatively high specific strength, electromagnetic shielding, vibration damping ability and dimensional stability. Due to their higher specific strength, outstanding castabil...
Magnesium alloys are commonly utilized as lightweight materials having significantly good physico-chemical properties such as relatively high specific strength, electromagnetic shielding, vibration damping ability and dimensional stability. Due to their higher specific strength, outstanding castability and excellent mechanical properties, magnesium alloys are used in a wide range of industries such as the automotive, aerospace and communication industries in order to meet the demands for environmental protection and energy saving requirements. However, magnesium-based alloys are susceptible to galvanic corrosion, and thus the widespread applications are severely limited. Fortunately, a series of surface modification techniques, such as electrochemical coating, chemical conversion coatings, hydride coating, anodizing, gas-phase deposition, laser surface alloying and polymer coating have been developed to improve the corrosion resistance of magnesium alloys over the last few decades. Among these techniques, plasma electrolytic oxidation (PEO) is a well-known technique for its ability to obtain high quality ceramic anodized coatings with perfect corrosion resistance, high hardness and good adhesion to substrates. AZ31B magnesium alloy is hardly oxidized by conventional anodizing techniques because of its (anodizing oxide layer) compact and dense surface, as compared with the case of cast materials (ex AZ91D). The plasma electrolytic oxidation seems to be more appropriate for AZ31B magnesium alloy than for AZ91D alloy because the former alloy has denser oxide surface layer. Although the remarkable progress has been made on the synthesis of the PEO coatings, very few researches on the effects of the compositions and microstructures of substrates on the formation and properties of the PEO coatings in cooperation with phosphating treatment are done, as existing reports on only anodized magnesium alloys pay more attention on developing optimization procedures for electrical parameters and electrolyte compositions. Plasma electrolytic oxidation has been applied to many magnesium products to improve their corrosion resistance. Generally, high voltage is applied in PEO process. However, such high voltage operation results in high cost and several other practical problems such as burning on edges of products because of high local current convergence as well as electric shock in working field. Moreover, the resultant anodized coatings generally consist of porous layer exhibiting low corrosion resistance. As a consequence, it is essential to find a solution for these drawbacks, which can be applicable in industrial field. In this work low PEO method was employed with constant low voltage as driving force for anodized film growth. However, low voltage PEO films have insufficient thickness for satisfactory corrosion resistance. In order to overcome this problem, pyrophosphate was added to electrolytic bath, and its effect on the corrosion resistance of the oxidized film was investigated for the PEO coatings in cooperation with phosphating treatment.
Magnesium alloys are commonly utilized as lightweight materials having significantly good physico-chemical properties such as relatively high specific strength, electromagnetic shielding, vibration damping ability and dimensional stability. Due to their higher specific strength, outstanding castability and excellent mechanical properties, magnesium alloys are used in a wide range of industries such as the automotive, aerospace and communication industries in order to meet the demands for environmental protection and energy saving requirements. However, magnesium-based alloys are susceptible to galvanic corrosion, and thus the widespread applications are severely limited. Fortunately, a series of surface modification techniques, such as electrochemical coating, chemical conversion coatings, hydride coating, anodizing, gas-phase deposition, laser surface alloying and polymer coating have been developed to improve the corrosion resistance of magnesium alloys over the last few decades. Among these techniques, plasma electrolytic oxidation (PEO) is a well-known technique for its ability to obtain high quality ceramic anodized coatings with perfect corrosion resistance, high hardness and good adhesion to substrates. AZ31B magnesium alloy is hardly oxidized by conventional anodizing techniques because of its (anodizing oxide layer) compact and dense surface, as compared with the case of cast materials (ex AZ91D). The plasma electrolytic oxidation seems to be more appropriate for AZ31B magnesium alloy than for AZ91D alloy because the former alloy has denser oxide surface layer. Although the remarkable progress has been made on the synthesis of the PEO coatings, very few researches on the effects of the compositions and microstructures of substrates on the formation and properties of the PEO coatings in cooperation with phosphating treatment are done, as existing reports on only anodized magnesium alloys pay more attention on developing optimization procedures for electrical parameters and electrolyte compositions. Plasma electrolytic oxidation has been applied to many magnesium products to improve their corrosion resistance. Generally, high voltage is applied in PEO process. However, such high voltage operation results in high cost and several other practical problems such as burning on edges of products because of high local current convergence as well as electric shock in working field. Moreover, the resultant anodized coatings generally consist of porous layer exhibiting low corrosion resistance. As a consequence, it is essential to find a solution for these drawbacks, which can be applicable in industrial field. In this work low PEO method was employed with constant low voltage as driving force for anodized film growth. However, low voltage PEO films have insufficient thickness for satisfactory corrosion resistance. In order to overcome this problem, pyrophosphate was added to electrolytic bath, and its effect on the corrosion resistance of the oxidized film was investigated for the PEO coatings in cooperation with phosphating treatment.
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