Final answer:
To create yellow rust on cast iron, which is iron oxide-hydroxide, FeO(OH)H₂O, an environment with consistently high moisture levels is required. While red rust, or iron (III) oxide, forms readily with vinegar, salt, and hydrogen peroxide, yellow rust formation is more nuanced and depends on specific environmental conditions.
Step-by-step explanation:
To create yellow rust (iron oxide-hydroxide) on cast iron, one typically needs to simulate conditions of high moisture such as those near significant standing water sources. The red rust you have encountered using a mix of vinegar, salt, and hydrogen peroxide is actually iron (III) oxide, or Fe₂O₃.
Yellow rust, on the other hand, contains iron (III) oxide-hydroxide FeO(OH)H₂O. The desired reaction involves the oxidation of iron in the presence of water, forming hydrated iron ions (Fe²⁺ (aq)) which further react with oxygen and water to eventually form the yellow rust. This process is influenced by the environment and the availability of water, oxygen, and other factors like the contact with different metals, which can accelerate corrosion.
While direct application of a specific chemical to produce yellow rust might be challenging, you could create conditions that would favor the formation of yellow rust over red rust. For example, maintaining a consistently high moisture environment around the cast iron, potentially by using wet sponges or cloths, may simulate the standing water conditions that favor yellow rust formation.
However, given that rust formation is a complex process highly dependent on environmental factors, collaboration with a chemist is a good approach for tailoring the circumstances that would generate the desired type of rust.