How to remove the scale of aluminum pot

First, aluminum will react with hydrochloric acid, whether it is concentrated or dilute hydrochloric acid. 2Al＋6HCl====2AlCl3＋3H2↑, so the A option is wrong.

Then, iron and aluminum can be quickly dissolved in dilute nitric acid or dilute sulfuric acid, but the dissolution phenomenon in cold concentrated nitric acid or cold concentrated sulfuric acid almost completely stops because of the passivation reaction. The so-called passivation reaction refers to the metal The surface is transformed into a state that is not easy to be oxidized, and the chemical stability of metals or alloys is significantly enhanced by some factors, which is called passivation. So the B option is not. (Nitric acid HNO3 Sulfuric acid H2SO4)

After the water containing minerals such as calcium (Ca) and magnesium (Mg) salts is boiled, part of the water evaporates, and calcium sulfate (CaSO4), which is not easy to dissolve, precipitates. The originally dissolved calcium bicarbonate (Ca(HCO3)2) and magnesium bicarbonate (Mg(HCO3)2) decompose in boiling water and release carbon dioxide (CO2), which becomes insoluble calcium carbonate (CaCO3) and hydrogen. Magnesium oxide (Mg(OH)2) also precipitates. This is scale, mainly calcium sulfate, sulfuric acid does not react with it, besides, concentrated sulfuric acid is a very annoying thing and is not volatile.

In summary, cold concentrated nitric acid D should be used.