实验探究铁被浓硫酸“钝化”的认识误区

Experimental Study on Misunderstanding of “Passivation” of Iron by Concentrated Sulfuric Acid

冷的浓硝酸无疑可以钝化Fe和Al,但是冷的浓硫酸仅可以钝化Al,而不能钝化Fe。实验证明,被冷的浓硫酸处理(所谓钝化)后的铁表面不是生成致密氧化膜,而是生成一层不溶于浓硫酸的FeSO4,致使内层金属不能与酸持续反应,从而使反应停滞。

Cold concentrated nitric acid can passivate Fe and Al, but cold concentrated sulfuric acid can only passivate Al, but not Fe. It has been proved that the surface of Fe treated with cold concentrated sulfuric acid(so called passivation) produces not a dense oxide film but a layer of FeSO4 insoluble in concentrated sulfuric acid which causes the inner metal to be unable to react with acid continuously thus causing the reaction to stop.