Protective Coatings – Appropriate Primer for Steelwork For new fabricated steelwork on site or in the shop, which primer is commonly specified to provide initial corrosion protection and good adhesion for subsequent coats?

Introduction:Steel exposed to the atmosphere rapidly oxidizes. A primer formulated to inhibit corrosion and promote adhesion is essential before applying intermediate and finishing coats. This question tests recognition of the standard primer type used for general steelwork in many specifications and schedules of rates.

Given Data / Assumptions:

• Substrate: structural steel sections and fabricated assemblies.
• Objective: early corrosion protection and a sound base for topcoats.
• Environment: typical building and light industrial exposure (non-specialty).

Concept / Approach:

Red oxide of iron primers are traditional shop/field primers that provide a compatible, adherent base for alkyd or other coating systems. While modern zinc-rich/epoxy systems are common for severe duty, red oxide primer remains a widely referenced baseline for general environments.

Step-by-Step Solution:

Verification / Alternative check:

Public works specifications and product datasheets list red oxide primers for structural steel in normal exposures; specialty primers are selected based on corrosivity category.

Why Other Options Are Wrong:

White lead mixes are obsolete/toxic and not standard primers today; cement and casein paints lack metal adhesion and corrosion inhibition; skipping primer is poor practice.

Common Pitfalls:

Assuming masonry primers or finish coats alone suffice on bare steel; ignoring surface preparation requirements (e.g., cleaning to standard).

Final Answer:

Oxide of iron (red oxide) primer