Abstract 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.
TIAN Bo-Wen, ZHU Hua-Ying, LIU Huai-Le, LIU Xiao-Yu. Experimental Study on Misunderstanding of “Passivation” of Iron by Concentrated Sulfuric Acid[J]. Chinese Journal of Chemical Education, 2020, 41(15): 92-93.
