Pre-painted Galvanized Steel (PPGI) is a composite metal sheet produced by continuously roll-coating an organic finish onto the surface of hot-dip galvanized steel—following chemical pretreatment—and subsequently curing it at high temperatures. It combines the structural strength of steel, the corrosion resistance of a zinc coating, and the aesthetic appeal and weather resistance of an organic finish. Consequently, it is currently the most widely utilized pre-coated metal material across the construction, home appliance, and transportation sectors. I. Basic Structure (Five-Layer Composite)
From inner to outer:
Substrate: Cold-rolled steel sheet (Q195, DX51D, etc.)
Hot-dip Galvanized Layer: Pure zinc coating (sacrificial anode protection; the core anti-corrosion layer)
Chemical Conversion Layer: Passivation film (enhances coating adhesion; prevents “white rust” on the zinc layer)
Primer: Epoxy / Polyester (enhances anti-corrosion properties and interlayer bonding)
Topcoat + Backcoat: Polyester, Silicon-Modified Polyester, PVDF, etc. (determines appearance, weather resistance, and corrosion resistance)
II. Core Performance Features
Dual Anti-Corrosion Protection: Zinc layer (cathodic protection) + organic coating (barrier isolation); offers a service life 50% to 100% longer than ordinary galvanized sheets.
Strong Weather Resistance: Resistant to UV radiation and aging; highly resistant to chalking and discoloration.
Rich Color Options: Standard colors (off-white, sea blue, brick red), custom colors, and special effects such as wood grain or stone patterns.
Excellent Processability: Can be cold-bent, stamped, cut, and lock-seamed without easily chipping or peeling.
Lightweight and High-Strength: Low self-weight allows for rapid construction; serves as an ideal substitute for wood or brick.
Economical and Eco-Friendly: Requires no post-installation painting; offers low maintenance costs and is fully recyclable.
III. Key Specifications and Parameters
Substrate: Hot-dip Galvanized Steel (Code: Z)
Zinc Coating Weight (Double-sided, g/m²):
Standard Grade: 120–180 g/m²
Exterior Architectural Grade: 180–275 g/m²
Thickness: 0.3–2.0 mm (Commonly 0.4–0.8 mm)
Width: 900–1550 mm (Commonly 1000 / 1200 mm)
Coating Type (by Weather Resistance Grade):
PE (Polyester): General-purpose grade; suitable for indoor or standard outdoor applications.
SMP (Silicon-Modified Polyester): Medium-to-high weather resistance; suitable for industrial buildings.
HDP (High-Durability Polyester): Strong weather resistance; suitable for coastal or industrial zones.
PVDF (Fluorocarbon): Ultra-high weather resistance (20–30 years); suitable for high-end architecture and curtain walls.
IV. Production Process Flow
Uncoiling → 2. Pre-treatment (Degreasing → Water Rinsing → Passivation → Drying)
Coating (Primer Roll Coating → Baking → Cooling → Topcoat Roll Coating → Secondary Baking)
Post-treatment (Film Lamination, Quality Inspection, Coiling)