(1. 內(nèi)蒙古工業(yè)大學材料科學與工程學院，呼和浩特 010051；
2. 中國科學院金屬研究所金屬腐蝕與防護實驗室，沈陽110016)
摘 要: 研究添加不同含量稀土釔(Y)的AZ91鎂合金在連續(xù)浸泡及干濕交替腐蝕環(huán)境中的腐蝕行為。結(jié)果表明：添加稀土Y的AZ91鎂合金，腐蝕形貌轉(zhuǎn)變?yōu)椤敖z狀”腐蝕；在連續(xù)浸泡溶液環(huán)境中，腐蝕沿著同一條“絲”發(fā)展。而在干濕交替腐蝕環(huán)境中，腐蝕主要在濕環(huán)境下產(chǎn)生和發(fā)展，在干環(huán)境下停滯。重新置入濕環(huán)境時，舊的腐蝕“絲”不會明顯發(fā)展，而會形成新的腐蝕“絲”，鎂合金表面“絲狀”腐蝕數(shù)量隨干濕交替循環(huán)腐蝕次數(shù)增加而增多。“絲狀”腐蝕形貌的形成是由于稀土添加降低了Al元素在晶界上的分布，使得表面析氫腐蝕不易受到阻礙，腐蝕以“腐蝕絲”末端持續(xù)析氫向前發(fā)展。電化學阻抗測試結(jié)果表明：干濕交替腐蝕環(huán)境中的電荷轉(zhuǎn)移電阻明顯低于連續(xù)浸泡環(huán)境中對應(yīng)的電荷轉(zhuǎn)移電阻，這是因為干濕交替過程中，薄液膜的存在延長了鎂合金的析氫時間，而干環(huán)境的干燥作用破壞了鎂合金表面膜的完整性。
關(guān)鍵字: 鎂合金；腐蝕；干濕交替；稀土；電化學阻抗
（1. College of Materials Science and Engineering, Inner Mongolia University of Technology, Hohhot 010051, China;
2.Laboratory for Corrosion and Protection, Institute of Metal Research,
Chinese Academy of Sciences, Shenyang 110016, China）
Abstract:The corrosion behavior of AZ91 magnesium alloys with different additions of rare earth yttrium under immersion and dry-wet cyclic environments was studied. The results show that the differences in corrosion morphologies can be found between AZ91 alloy and the alloys with Y additions. The corrosion morphology of the original AZ91 alloy is featured with localized corrosion morphology while the corrosion morphologies of the alloys with Y additions are characterized by filiform corrosion feature. The corrosion extends along the same “l(fā)ine” when the alloys with Y addition are exposed to the immersion environment.However, the corrosion just initiates and develops in wet cyclic period, and suspends during the dry cyclic period when they are exposed to dry-wet cyclic environment. Besides, when the magnesium alloys with Y additions are exposed to the wet environment again, the original filiform corrosion does not extend any more, but new filiform corrosion can be found in other location. With the increase of dry-wet cycles, the number of filiform corrosion on the surface of magnesium alloys increases. The effect of rare earth Y on refining the grain of secondary phase and decreasing the Al distribution along the grain boundaries of the secondary phase leads that hydrogen evolution can not be impeded easily, and corrosion develops in the way of continued hydrogen evolution along the end of corrosion location. This is the reason why the filiform corrosion morphologies form. Electrochemicalimpedance spectra measurements indicate that the charge transfer resistance tested in dry-wet cyclic environment is much lower than that in immersion environment, suggesting that the magnesium alloys suffer heavier corrosion in dry-wet cyclic environment, which is relate to that the time of hydrogen evolution is prolonged under thin electrolyte layers and the integrity of the surface film of magnesium alloy is broken because of the drying effect under dry environment.
Key words: magnesium alloy; corrosion; dry-wet cyclic; rare earth; electrochemical impedance spectroscopy
