Which alloying element is commonly added to steel to enhance its corrosion resistance?

Chromium is commonly added to steel to enhance its corrosion resistance, primarily due to its ability to form a protective oxide layer on the surface of the steel. This oxide layer acts as a barrier that prevents moisture and oxygen from reaching the underlying steel, significantly reducing the chances of rust and further corrosion. This property is particularly evident in stainless steel, which contains a minimum of 10.5% chromium, and is well-known for its durability and resistance to rust and stains.

Nickel does play a role in improving the toughness and impact resistance of steel but is not as effective as chromium when it comes to enhancing corrosion resistance. Molybdenum is typically used to increase hardness and toughness and to improve resistance to pitting corrosion, particularly in high-temperature applications. Copper can also provide some degree of corrosion resistance but is generally less effective than chromium in this context. Thus, while other alloying elements have their benefits, chromium stands out as the key element specifically linked to enhancing corrosion resistance in steel.