Furukawa-Sky Review No.9 (April 2013)

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技術論文

アルミニウム合金の腐食試験における酢酸の孔食促進効果
Effects of Acetic Acid on Pitting Corrosion Acceleration in Corrosion Tests of Aluminum Alloys

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• 大谷　良行
  Yoshiyuki Oya
• 兒島　洋一
  Yoichi Kojima

促進腐食試験におけるアルミニウムの腐食挙動に及ぼす酢酸の影響を電気化学的測定および自然浸漬試験により調査した。孔食電位の比較的貴なAl-1 mass%Mn合金の孔食は，溶存酸素の還元反応を主なカソード反応として進行し，その腐食速度は酢酸添加量に依存しない。一方，孔食電位の卑なAl-Zn合金の孔食は，水素イオンの還元反応を主なカソード反応として進行し，その腐食速度は酢酸添加量とともに増大する。酢酸がアルミニウム合金の孔食を促進する理由は，pHの低下よ りも酸解離定数の小さい酢酸が水素イオンのキャリヤとして働くことによる。

Effects of CH₃COOH on the corrosion behavior for aluminum alloys during accelerated corrosion tests were investigated. Based upon polarization curves, the dominant cathodic reaction for pitting corrosion of Al-Zn alloys was reduction of hydrogen ion because their pitting potentials were less noble, while that of Al-1 mass%Mn alloy, whose pitting potentials were relatively noble, was reduction of dissolved O₂. While the corrosion rate for the Al-Zn alloys were also increased with the concentration of CH3COOH, that for Al-1 mass%Mn alloy were independent of the concentration of CH₃COOH. It is indicated that corrosion rate for Al-Zn alloys is related to the concentration of CH₃COOH added in the solutions. The relation between the corrosion rate and concentration of CH₃COOH were confirmed from immersion tests. The reason for increase in the corrosion rate for the Al-Zn alloys is due to that CH3COOH acts as a hydrogen ion carrier rather than agent of lowering pH. The concentration of CH₃COOH is should be standardized but not the pH to increase the reproducibility of the corrosion tests.

技術論文 / Technology Articles

1. High Strain Rate Blow Formability of Newly Developed Al-Mg-High-Mn Alloy
2. Al-Mg-Si系合金の再結晶集合組織形成に及ぼす冷間圧延率の影響 Effect of Cold Rolling Reduction on Development of Recrystallization Textures in an Al-Mg-Si Alloy
3. ろう付加熱後に180℃熱処理したAI-Mn-Cu系合金の粒界腐食感受性 Intergranular Corrosion Susceptibility for AI-Mn-Cu Alloys Subjected to Heat Treatment at 180℃ after Brazing Process
4. アルミニウム合金の腐食試験における酢酸の孔食促進効果 Effects of Acetic Acid on Pitting Corrosion Acceleration in Corrosion Tests of Aluminum Alloys
5. Al-Mn系合金のしきい応力に及ぼすマグネシウム添加の影響 Effects of Magnesium Addition on Threshold Stress of Al-Mn Alloys