It's not. In high school, there are only cold concentrated H2SO4 and concentrated HNO3, and the passivation principle is to form a dense oxide film on the surface of iron or aluminum to prevent further reaction of the acid on the metal (if it is hot, it will destroy the oxide film) and the concentration must be high, like 98%H2SO4 on the base is H2SO4 molecules and only a small amount of H will cause H to react with iron or aluminum. So in high school, only those two fit the bill