PPGI (Pre-Painted Galvanized Iron) and PPGL (Pre-Painted Galvalume Steel Coil) are two common pre-painted metal coils, widely used in construction, home appliances, automobiles and other industries. Although they are similar in appearance, there are significant differences in substrate material, corrosion resistance, heat resistance, cost, etc.

1. Different substrate materials

(1) PPGI (color-coated galvanized steel coil)

Substrate: hot-dip galvanized steel sheet (GI, Galvanized Iron)

Coating: pure zinc (Zn) coating, zinc content ≥ 99%

Coating weight: usually the double-sided galvanizing amount is between 40~275g/m²

(2) PPGL (color-coated galvanized steel coil)

Substrate: galvanized steel sheet (GL, Galvalume)

Coating: aluminum-zinc alloy (55% aluminum + 43.4% zinc + 1.6% silicon)

Coating weight: usually the double-sided galvanizing amount is between 50~150g/m²

Core difference:

PPGI's coating is pure zinc, while PPGL's coating is aluminum-zinc alloy, so PPGL has better corrosion resistance and heat resistance.

2. Performance comparison

(1) Corrosion resistance

PPGI: The zinc layer provides sacrificial anode protection, but white rust (zinc corrosion) is prone to occur in high-salt and high-humidity environments.

PPGL: In the aluminum-zinc alloy coating, aluminum forms a dense oxide film (Al₂O₃), which is 2 to 6 times more corrosion-resistant than pure zinc, and is particularly suitable for areas with marine climate or heavy industrial pollution.

(2) Heat resistance

PPGI: Zinc has a low melting point (about 420°C) and is easily oxidized at high temperatures. The long-term use temperature is recommended to be ≤200°C.

PPGL: Aluminum has a high melting point (660°C), and aluminum-zinc-plated steel sheets can withstand higher temperatures (≤315°C) and are suitable for high-temperature environments (such as chimneys, ovens, etc.).

(3) Appearance and processability

PPGI: The zinc layer is softer and has better stamping formability, but the surface is easily scratched.

PPGL: The aluminum-zinc coating is harder and has better wear resistance, but microcracks may occur during stamping, and mold parameters need to be adjusted.

(4) Cost

PPGI: The cost of galvanizing is low and it is suitable for projects with limited budgets.

PPGL: The cost of galvanizing is higher, but it has a longer life and a higher overall cost-effectiveness.

3. Main application areas

Main application scenarios

PPGI light buildings (color steel tiles, sandwich panels), home appliance shells, general industrial equipment

PPGL high corrosion environment (coastal buildings, chemical plants), high temperature environment (chimneys, ovens), high-end building curtain walls

4. How to choose?

Choose PPGI in the following situations:

Budget is limited and used in ordinary environments

Good molding processability is required (such as stamping parts)

Short-term use or non-high corrosion areas

Choose PPGL in the following situations:

High salt, high humidity, high pollution environment (such as coastal areas, industrial areas)

High temperature applications (such as industrial furnaces, flues)

Long-term use, pursuit of lower maintenance costs

5. Conclusion

The main difference between PPGI and PPGL is the coating composition. PPGL (aluminum zinc plating) is superior to PPGI (galvanizing) in corrosion resistance and heat resistance, but the cost is higher. When choosing, you need to comprehensively consider factors such as the use environment, budget, and processing requirements.

If it is an ordinary building or home appliance, PPGI is economical and practical; if it is a highly corrosive or high-temperature environment, PPGL is more reliable and more cost-effective for long-term use.