Difficulty: Easy
Correct Answer: Red lead
Explanation:
Introduction / Context:
Before finishing coats are applied to metal, a primer promotes adhesion and provides corrosion protection. Historically in civil works, red lead primer (lead tetroxide-based) has been widely used for iron and steel to resist rusting and enhance topcoat durability. This question checks recognition of that standard base coat in traditional specifications.
Given Data / Assumptions:
Concept / Approach:
Red lead primers provide good adhesion and corrosion resistance on steel due to their barrier properties and chemical passivation tendencies. While alternatives like zinc-rich primers and epoxy systems are common today, traditional exam answers still emphasize red lead for “commonly used base.”
Step-by-Step Solution:
Verification / Alternative check:
Older standard specifications and handbooks list red lead primer for ferrous metals, preceding widespread adoption of modern zinc/epoxy systems.
Why Other Options Are Wrong:
Zinc white / White lead / Titanium white: These are primarily pigments for color/opacity; they do not serve as classic anti-corrosive primers for ferrous metals in the traditional sense.
Common Pitfalls:
Confusing color pigments with anti-corrosive primers; overlooking historical context versus modern low-VOC, lead-free systems.
Final Answer:
Red lead
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