What is the difference between stainless steel and iron?

Stainless steel and iron are both metallic materials, but they differ in composition, properties, uses, and appearance:

Iron: Iron is a chemical element with the symbol Fe. Pure iron contains a high proportion of iron atoms, usually above 99%. However, in practical applications, iron is often alloyed with other elements to improve its properties. For example, carbon steel is an alloy of iron and carbon, with a carbon content ranging from 0.02% to 2.11%.

Stainless steel: Stainless steel is an alloy of iron, chromium, nickel, and other elements. The chromium content in stainless steel is generally not less than 10.5%, which forms a dense chromium - rich oxide film on the surface of the metal, giving it excellent corrosion - resistance.

Mechanical properties: Pure iron is relatively soft and has low strength. Although the strength of carbon steel can be increased by adjusting the carbon content, its corrosion - resistance is poor. Stainless steel, on the other hand, has high strength, good toughness, and excellent corrosion - resistance. It can maintain its mechanical properties and appearance for a long time in harsh environments.

Physical properties: Iron has a relatively high density of about 7.87 g/cm³. Its thermal conductivity and electrical conductivity are also relatively good. Stainless steel has a similar density to iron, but its thermal conductivity is slightly lower than that of iron. This is because the alloying elements in stainless steel affect its thermal conductivity.

Applications

Iron: Iron and its alloys are widely used in construction, machinery manufacturing, and automotive industries. For example, carbon steel is commonly used to make building structures, machine parts, and automobile bodies due to its high strength and low cost.

Stainless steel: Due to its excellent corrosion - resistance, stainless steel is widely used in the food processing, medical, and chemical industries. In the food processing industry, stainless steel equipment and utensils are used because they are easy to clean and do not contaminate food. In the medical field, stainless steel is used to make surgical instruments and implants.

Iron: Iron usually has a grayish - black appearance. When exposed to air and moisture, iron is prone to rust, forming a reddish - brown iron oxide layer on its surface.

Stainless steel: Stainless steel has a shiny silver - white appearance. Due to the formation of a protective oxide film on its surface, stainless steel does not rust easily, maintaining its bright appearance for a long time.