PPGI (Pre-Painted Galvalume Steel Coil/Sheet) is a pre-painted aluminum-zinc coated steel sheet, which combines the corrosion resistance of the aluminum-zinc coated substrate and the decorative/protective performance of the color coating. It is widely used in construction, home appliances and other fields. The following are its key knowledge points:

1. Substrate material: Galvalume (aluminum-zinc coated)

PPGI's metal substrate is aluminum-zinc coated steel sheet (55% aluminum, 43.4% zinc, 1.6% silicon), and its performance is better than ordinary galvanized sheet (GI):

Corrosion resistance: The corrosion resistance of aluminum-zinc coated steel is 2 to 6 times that of galvanized sheet (especially in high temperature and high humidity environments).

Heat resistance: It can withstand high temperatures of 300°C for a long time (galvanized sheet is only about 200°C).

Reflectivity: The aluminum layer reflects ultraviolet rays and delays the aging of the coating.

2. Coating structure (five-layer composite)

Primer (epoxy resin/polyester) 5~10μm

Topcoat (PVDF/polyester/SMP) 15~25μm

Chemical conversion layer (chromate/chrome-free) 0.1~0.5μm

Alu-zinc coating (Galvalume) 20~150g/m²

Rolled steel substrate 0.3~1.2mm

Coating type comparison:

PVDF (fluorocarbon): super weather-resistant (more than 20 years), UV-resistant, used for high-end building curtain walls. Polyester (PE): low cost, rich colors, suitable for home appliances and interior decoration.

SMP (silicon-modified polyester): weather resistance is between PVDF and PE.

3. Core performance indicators

Corrosion resistance:

Salt spray test (alu-zinc coating substrate): ≥1000 hours (red rust appearance time).

The scratch expansion width of the color-coated plate is ≤2mm (ASTM D1654).

Adhesion: Cross-hatch test level 0 (no peeling).

Hardness: Pencil hardness ≥ H (PVDF coating can reach 2H).

Temperature resistance: -40°C~120°C without cracking.