初期腐蝕行為
( 1．北京科技大學(xué)材料科學(xué)與工程學(xué)院 腐蝕與防護(hù)中心， 北京 100083；
2．中國科學(xué)院 金屬研究所金屬腐蝕與防護(hù)國家重點(diǎn)實(shí)驗(yàn)室， 沈陽 110016)
摘 要: 采用室內(nèi)加速的方法， 利用金相顯微鏡、掃描電鏡和X射線衍射等手段對AZ91D鎂合金在含微量SO2工業(yè)污染環(huán)境中的初期腐蝕層形貌以及腐蝕產(chǎn)物進(jìn)行了分析和研究。結(jié)果表明： SO2加速鎂合金的腐蝕，隨著SO2含量增加， 鎂的腐蝕速率加快。鎂合金的初期腐蝕具有局部腐蝕的特征。 腐蝕優(yōu)先從α相基體開始，腐蝕初期在材料表面生成一層保護(hù)性的含有MgO和Mg(OH)2的薄膜。 SO2降低了薄液層的pH值， 增強(qiáng)溶解過程， 促進(jìn)可溶性MgSO3·6H2O和MgSO4·6H2O腐蝕產(chǎn)物的生成， 使表面膜失去保護(hù)作用，加速鎂合金的后期腐蝕。
關(guān)鍵字: SO2；大氣環(huán)境； AZ91D鎂合金； 腐蝕
（ 1. Corrosion and Protection Center, School of Materials Science and Technology, University of Science and Technology Beijing, Beijing 100083, China;
2. State Key Laboratory for Corrosion and Protection, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China）
Abstract: The initial surface morphology of corrosion layer, corrosion products and structure of rust layer for AZ91D magnesium alloy in SO2 industrial polluted atmosphere were analyzed by metallographic observation, SEM and XRD. The results show that corrosion rate increases with increasing SO2 content in the atmosphere. The initial attack has the characteristics of localized corrosion. Corrosion starts from α phase, and MgO and Mg(OH)2 form at first, which provide a protective layer. SO2 decreases pH in the electrolyte layer, accelerates dissolution process, and promotes the formation of MgSO3·6H2O and MgSO4·6H2O. These soluble corrosion products result in the loss of protection function and the acceleration of corrosion. Meanwhile, cracks appear with continuation of corrosion, which provide the paths for oxygen and other corrosion pollutants filtering into matrix, further resulting in severe localized corrosion.
Key words: SO2; atmosphere; AZ91D magnesium alloy; corrosion
