Which addition imparts resistance to atmospheric corrosion in steel?

Copper is known for its excellent resistance to atmospheric corrosion in steel when added as an alloying element. This is largely due to the formation of a protective patina that develops on the surface of the steel when exposed to moisture and oxygen. This patina acts as a barrier, preventing further corrosion by limiting the access of corrosive agents to the underlying metal.

In addition to enhancing corrosion resistance, copper can also enhance the mechanical properties of steel, such as strength and toughness. This makes copper a desirable addition in various applications where longevity and durability in challenging environments are crucial.

While other elements, such as manganese and aluminum bronze, provide specific benefits in terms of strength and wear resistance, they do not significantly enhance atmospheric corrosion resistance to the extent that copper does. Hence, copper stands out as the most effective choice for imparting such resistance in steel.