How to Paint IBR Sheeting Without Primer Adhesion Failure

Using incorrect primer on galvanised IBR sheeting causes adhesion failure and premature coating breakdown, requiring costly repainting of entire roof sections.

1. Surface Preparation for New IBR Sheeting

Remove all dust and dirt from the galvanised surface. Clean with galvanised iron cleaner or sugar soap solution to eliminate manufacturing residues and oils. Rinse thoroughly with clean water to remove all cleaning solution residues. Allow the surface to dry completely before applying primer — moisture under the primer film will cause adhesion problems.

2. Surface Preparation for Previously Painted IBR

Remove flaky or peeling paint with a scraper or wire brush, stripping only the failing areas rather than all existing paint. Remove rust patches with a scraper or wire brush to expose clean metal. Clean the entire surface with sugar soap solution to remove dust, grime, and oils — use a broom on large roof surfaces for efficient coverage. Rinse thoroughly with clean water and allow to dry completely.

3. Primer Selection and Application

Apply GI Primer formulated specifically for galvanised iron and zinc-coated steel surfaces. Do not use red oxide or FPW15 primers on galvanised iron as adhesion failure will result. For new unpainted IBR, apply a full coat of GI Primer to the entire surface. For previously painted IBR, spot-prime only the raw metal exposed during scraping. Apply primer by roller, roof renovator brush, or spray equipment. Allow primer coat to dry completely before topcoat application.

4. Topcoat Application Technique

Apply topcoat using high-gloss enamel, super-gloss enamel, or QD enamels spray over the GI Primer base. Use roller, brush, or spray application methods. Do not paint in direct sunlight or high wind conditions as rapid drying causes uneven film formation and poor adhesion. Maintain a wet edge by working in manageable sections to avoid lap marks on large roof surfaces. Work from ridge downward toward gutters for consistent coverage pattern. Allow full dry time between coats to prevent solvent entrapment and blistering.

Key Insights

GI Primer is essential for galvanised IBR surfaces — standard primers cause adhesion failure. Proper surface preparation removes contaminants that prevent primer bonding. Environmental conditions during application directly affect film quality and adhesion performance. Working ridge to gutter ensures consistent coverage and prevents visible application marks.