Corrosion tendencies — which combined statement correctly summarizes oxidation/rusting behavior among common ferrous materials? Choose the best option.

Difficulty: Easy

Correct Answer: All of the above

Explanation:


Introduction / Context:
Rusting of ferrous materials involves oxidation in the presence of moisture and oxygen. The microstructure and composition (carbon, alloying, slag inclusions) influence how quickly different iron-based materials corrode in typical atmospheres.


Given Data / Assumptions:

  • Ordinary atmospheric exposure is considered.
  • Materials: cast iron, steel, wrought iron.
  • Qualitative comparison of relative oxidation tendencies.


Concept / Approach:
Rust (hydrated iron oxides) forms readily on steel. Cast iron, with higher carbon and graphite, often corrodes more slowly in uniform exposure due to graphitic layers acting as a partial barrier. Wrought iron, containing slag stringers, shows moderate corrosion behavior compared to the other two. All statements A–D are thus concurrently valid as a general qualitative summary.


Step-by-Step Solution:

1) Define rust: hydrated iron oxides formed during atmospheric corrosion.2) Compare materials: steel > wrought iron > cast iron in typical oxidation rate.3) Confirm that cast iron often shows better general corrosion resistance than mild steel.4) Synthesize: all listed statements align with the qualitative hierarchy.


Verification / Alternative check:
Materials engineering texts describe cast iron’s graphitic corrosion and steel’s higher rusting rate in many environments, with wrought iron intermediate.


Why Other Options Are Wrong:
Any single-statement option omits the correctness of the remaining true assertions; only the aggregate option captures the complete, commonly taught comparison.


Common Pitfalls:
Assuming one rule fits all corrosive environments; chloride-rich or acidic conditions can change relative performance, but the general trend holds for typical atmospheres.


Final Answer:
All of the above

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