Protective primers – commonly used base coat for iron and steel work Which base (primer) is most commonly used for protecting iron and steel in building works?

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:

  • Context is traditional building practice and exam-oriented references.
  • Modern health and environmental restrictions are acknowledged but not the focus of this item.
  • The primer is intended for ferrous substrates.


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:

1) Identify substrate: iron/steel requires corrosion-inhibitive primer.2) Traditional choice: red lead has long been specified in classic building texts.3) Conclude red lead is the commonly used base coat in the traditional framing of the question.


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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