GI vs Galvalume vs PPGI Sheets: Which Coated Steel to Choose
Galvanized (GI), Galvalume (GL, AZ) and pre-painted (PPGI/PPGL) steel sheets compared: coatings, heat and corrosion resistance, appearance, cost and uses in Saudi Arabia.
Saudi Steel Work Editorial Team · · 3 min read
Short answer: GI sheet has a pure zinc coating and is versatile and easy to fabricate. Galvalume (about 55% aluminium, 43% zinc) generally lasts longer in many atmospheres and reflects heat well, making it popular for roofing. PPGI and PPGL are GI or Galvalume with a factory paint system for colour and extra protection.
Coated steel sheets are everywhere in Saudi buildings — roofs, walls, ducts, panels and enclosures. The three main options are GI, Galvalume and pre-painted steel.
GI (galvanized iron)
- Coating: pure zinc (Z designations, e.g. Z275)
- Strengths: good cut-edge protection, easy to weld and form, widely available
- Uses: ducting, purlins, decking, general fabrication, substrate for paint
See galvanized coatings explained.
Galvalume (GL / AZ)
- Coating: about 55% aluminium, 43.4% zinc, 1.6% silicon (AZ designations, e.g. AZ150)
- Strengths: typically longer atmospheric life than GI of similar coating mass; better heat reflectivity
- Limitations: less sacrificial protection at cut edges; avoid contact with wet concrete; not ideal for heavy welding
- Uses: roofing, wall cladding, substrate for PPGL
PPGI / PPGL (pre-painted)
- Coating: GI or Galvalume substrate + primer + finish coat applied on a coil coating line
- Strengths: colour, appearance, extra barrier protection
- Paint systems: polyester, SMP, PVDF (paint system guide)
- Uses: visible roofs and facades, sandwich panels, interiors
Comparison
| Factor | GI | Galvalume | PPGI / PPGL |
|---|---|---|---|
| Appearance | Spangled/silver | Silver, matte | Coloured |
| Heat reflectance | Moderate | High | Depends on colour |
| Cut-edge protection | Good | Fair | Depends on substrate |
| Weldability | Good | Limited | Poor (paint) |
| Typical use | Fabrication, ducts | Roofs, cladding | Visible envelopes |
Recommendations for Saudi Arabia
- Roofs inland: Galvalume or light-coloured PPGL for heat reflection
- Coastal facades: PPGL/PPGI with SMP or PVDF and adequate substrate coating
- Ducts and hidden steel: GI
- Fabricated items to be welded: GI, then touch-up
Explore roofing and cladding and steel sheets.