Compared with carbon steel and iron, iron is easy to rust.
Iron is not easy to react with oxygen, sulfur, chlorine and other non-metallic elements in dry air. If there are impurities, it will rust easily in humid air; it will rust faster in humid air with acid, alkali or salt solution .
Iron is easily soluble in dilute inorganic acids to form divalent iron salts and release hydrogen. When meeting concentrated sulfuric acid or concentrated nitric acid at room temperature, a layer of oxide protective film is formed on the surface to "passivate" iron, so iron products can be used to hold cold concentrated sulfuric acid or cold concentrated nitric acid. When heated, iron can react with concentrated sulfuric acid or concentrated nitric acid to generate +3-valent iron salt, and simultaneously generate SO2 or NO2.