Not only iron can be passivated, but other metals can also be passivated, such as Cr (chromium), Ni (nickel), Co (cobalt), Mo (molybdenum), Al (aluminum), Ta (tantalum), Nb ([font] niobium [font]) and W (tungsten), etc. The most easily passivated metals are Cr (chromium), Mo (molybdenum), Al (aluminum), Ni (nickel), and Fe (iron).
Not only concentrated nitric acid can passivate metals, but other strong oxidants such as concentrated sulfuric acid, (high) chloric acid, (hydrogen) iodic acid, potassium dichromate, potassium permanganate acid solution, etc., can cause metal passivation.
In individual cases, a few metals can be passivated in non-oxidizing media, such as magnesium in HF (hydrofluoric acid), molybdenum and niobium in HCl (hydrochloric acid).
Iron and aluminum can be quickly dissolved in dilute HNO3 or dilute H2SO4, but the dissolution phenomenon in concentrated HNO3 or concentrated H2SO4 is almost completely stopped, carbon steel is usually easy to rust, if the appropriate amount of Ni and Cr is added to the steel, it becomes stainless steel. A phenomenon in which the chemical stability of metals or alloys is significantly enhanced by some factors is called passivation. The phenomenon of metal passivation caused by certain passivating agents (chemicals) is called chemical passivation.