My answer is that iron pots can't be used to cook Chinese medicine, and stainless steel is not suitable for cooking Chinese medicine.

The best traditional Chinese medicines for decocting drugs are casserole, ceramics and crock (metal containers can transfer heat and dissipate heat faster, and ceramics have better thermal insulation performance, which can reduce heating energy). It is forbidden to use iron and bronze utensils, and it is not recommended to use aluminum utensils (although the surface of aluminum utensils will produce a dense aluminum oxide protective layer, due to long-term boiling or scrubbing with steel balls, trace aluminum will enter the human body, which is harmful to health).

Iron can easily change chemically with tannins of rhubarb, Polygonum Multiflori Radix, Radix Paeoniae Alba, Sanguisorba officinalis, hematoxylin, Galla Chinensis and other traditional Chinese medicines, thus changing the color and even the medicinal properties of the decoction. Iron soup contains rust smell, which is easy to cause nausea and vomiting when taking medicine.

Iron is beneficial in daily cooking and eating, because iron will release trace ferrous ions when heated, and ferrous ions are needed by human blood, especially red blood cells. Lack of ferrous ions can lead to anemia. However, when iron is used to decoct traditional Chinese medicine, iron ions will react with the chemical components of traditional Chinese medicine, which will affect the efficacy. Stainless steel is also a kind of iron, but adding some components such as chromium and nickel to iron will also affect its efficacy. It can be said that there is no big consequence, but the effect is certain.

Due to the stable chemical properties of ceramics, the adverse chemical reaction between medicine and pot can be reduced or avoided in long-term pain, thus maintaining the inherent properties of medicine and improving the due curative effect of medicine.