Question

Stainless steel contains iron and

• A. Cr + Ni
• B. Cr + Zn
• C. Zn + Pb
• D. Fe + Cr + Ni

Answer 1

The Correct Option is A

Stainless steel is a widely used alloy, renowned for its corrosion resistance and mechanical properties. The primary composition of stainless steel involves three key elements: iron (Fe), chromium (Cr), and nickel (Ni). Let us explore the contribution of each element in stainless steel:

• Iron (Fe): It is the base metal and provides the fundamental metallurgical properties to the alloy.
• Chromium (Cr): This element is crucial as it forms a chromium oxide layer on the surface, which prevents further surface corrosion by blocking oxygen diffusion to the steel’s surface and stops corrosion from spreading into the metal’s internal structure.
• Nickel (Ni): It enhances the corrosion resistance further and provides an austenitic (face-centered cubic crystal structure) phase to the alloy, increasing its toughness and workability.

Given the options:

• Cr + Ni: This combination (chromium and nickel) is essential in stainless steel as outlined above.
• Cr + Zn: Zinc is not typically part of stainless steel's formulation.
• Zn + Pb: Neither zinc nor lead are part of the standard composition of stainless steel.
• Fe + Cr + Ni: This option lists the complete primary composition of stainless steel but exceeds the elements specified in the question.

The correct answer is Cr + Ni as these elements are crucial for stainless steel's defining characteristics apart from iron.