Stainless steel contains iron, chromium, and often nickel. Which element provides the corrosion resistance?
A. Iron
B. Nickel
C. Carbon
D. Chromium
Answer: Option D
Solution (By JKExamLibrary)
Chromium (minimum 10.5%) forms a thin, adherent, transparent oxide layer (Cr₂O₃) on the surface, preventing further oxidation. Nickel adds ductility and enhances corrosion resistance. Iron is the base; carbon is for hardness but not corrosion resistance.
Explanation:
Graphite conducts electricity due to delocalized electrons in its structure and is chemically inert, allowing its use in electrodes for electrolysis and batteries. Diamond is an insulator. Hardness is not the reason; graphite is soft. It is opaque and black. Graphite electrodes are used in arc furnaces.
Explanation:
The thermite process involves the reduction of a metal oxide by aluminum powder, which is highly exothermic. It is used to extract metals like chromium, manganese, and iron from their oxides (e.g., Cr2O3 + 2Al -> 2Cr + Al2O3). It is also practically used for welding iron railway tracks.
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