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一、铝为什么会受食盐的腐蚀?铝是一种活泼的金属,在空气中会迅速被氧化,生成一层具有保护作用的氧化膜。这氧化膜与金属铝同晶,都是面心立方密堆积。由于氧化膜的存在,使铝的还原电位从-1.66伏升高至+0.6伏。在氧化膜层中,氧离子的半径大于铝原子半径,这就使得在金属铝和氧化膜层之间能够形成一个理想的空隙。当介质中存有 Cl~-离子和晶体表面产生缺陷时,偶然出现在氧化膜层中的 Cl~-离子,将严重地破坏金属铝和氧化膜层之间的结晶连续性,这样,氧化膜则破裂,金属铝便进一步被氧化。这就是 Cl~-离子腐蚀铝的主要原因。
First, why aluminum corrosion by salt? Aluminum is a lively metal, the air will be rapidly oxidized, generating a layer of protective oxide film. This oxide film is crystallized with metallic aluminum, all with a face-centered cubic packing. Due to the presence of the oxide film, the reduction potential of aluminum is raised from -1.66 V to +0.6 V. In the oxide layer, the radius of the oxygen ions is larger than the radius of the aluminum atoms, which makes it possible to form a desired void between the aluminum metal and the oxide layer. When Cl - ions exist in the medium and defects are formed on the surface of the crystal, Cl ~ - ions that occasionally appear in the oxide film layer will severely damage the crystal continuity between the metal aluminum and the oxide film layer. Thus, the oxide film Then rupture, aluminum is further oxidized. This is the main reason for Cl ~ - ion corrosion of aluminum.