Alloying ____ elements in steel improves resistance to corrosion and oxidation. 

Explanation:

Chromium is one of the important metals which is used to improve the following characteristics of a material.

• To increase the abrasion resistance
• To provide the better hardness
• To improve the corrosion and the oxidation resistance
• To improve the temperature resistance
• With high C resists wear and abrasion

Nickel: It is an austenite stabilizer, it increases the corrosion resistance of steel, it also increases impact resistance at low temperatures.

Effect of other alloying elements on steel: 

Manganese is used to improve the hardness and strength of the material. It also acts as a desulfurizing agent.

Vanadium is used to refine grain size. Steels containing vanadium have a much finer grain structure than steels of similar compositions without vanadium. Vanadium is used to improve the mechanical properties of the materials such as hardness and toughness.

Cobalt improves strength at high temperatures and magnetic permeability. It contributes to red hardness by hardening ferrite. It is an alloying element in certain high-speed steels. Cobalt is used in martensitic steels, where it increases hardness and tempering resistance, especially at higher temperatures.