Analysis of the 5 core differences between PPGI steel sheets and PPGL steel coils

PPGI steel plates and PPGL steel coils are often confused in steel procurement, but they differ significantly in practical applications. Understanding these 5 key points will help you make more informed purchasing decisions. Maxwell Steel, as a professional steel supplier, explains the core differences between PPGI and PPGL to help you select the right materials.

1. Differences in basic definitions and product forms

PPGI (Pre-Painted Galvanized Iron) refers to pre-coated galvanized steel sheet, usually delivered in flat form, with a thickness ranging from 0.12mm to 1.5mm. It is suitable for applications requiring high flatness, such as building exterior walls and appliance panels. PPGL (Pre-Painted Galvanized Steel Coil), on the other hand, is pre-coated galvanized steel coil, supplied in coil form, with a typical thickness of 0.3mm to 3.0mm. It is more suitable for continuous processing lines such as color-coated sheet forming and pipe manufacturing.

    Key identifying features:

• PPGI is pre-cut at the factory, resulting in finer edge treatment.

• PPGL rolls typically weigh 3-20 tons per roll and require unwinding equipment.

• PPGI surface coating uniformity tolerance is ±2μm, while PPGL allows ±3μm due to subsequent processing.

2. Comparison of Coating Structure and Corrosion Resistance

  Although both use a zinc base coat, PPGI typically uses a pure zinc coating with a zinc content ranging from 60-275 g/m², achieving a salt spray test duration of 500-1000 hours. PPGL, on the other hand, more often uses a zinc-iron alloy coating, which offers stronger adhesion and is suitable for subsequent stamping deformation. However, its corrosion resistance is slightly lower than that of the pure zinc coating, with a salt spray test duration of 300-800 hours under the same conditions.

3. Coating process and color performance

PPGI typically employs a reverse roll coating process, resulting in a coating thickness of 15-25 μm, achieving high gloss (≥80 GU at an 85° angle) and fine texture. PPGL, on the other hand, commonly uses curtain coating, producing a thicker coating (20-35 μm), but with gloss controlled at 60-75 GU. This design helps prevent coating cracking during subsequent molding. Regarding color difference control:

• PPGI ΔE≤1.0（CIE LAB Standard）
• PPGL ΔE≤1.5（Considering subsequent processing deformation）

4. Mechanical Properties and Processing Adaptability

PPGL steel coils typically use SPCC or DX51D+Z materials as the substrate, with a yield strength of 140-280MPa and an elongation of ≥22%, making them particularly suitable for processing scenarios requiring multiple bending and forming. PPGI, on the other hand, uses higher-strength substrates such as SGH340 or SGH400, with a yield strength reaching 340-400MPa, but the elongation is reduced to 12-18%, making it more suitable for static load-bearing structural components.

Processing Precautions:

• PPGL continuous stamping speed can reach 60 times/minute.

• PPGI shearing requires maintaining a tool gap ≤ 8% of the plate thickness.

• Both types of welding are recommended to use laser welding or pulsed MIG welding.

5. Cost Factors and Procurement Strategy

In terms of price per ton, PPGL coils are typically 5-8% cheaper than PPGI flat sheets, but the following hidden costs must be considered:

• Uncoiling loss: PPGL requires cutting 1-2 meters from each end, resulting in a loss rate of approximately 3%.

• Storage requirements: PPGL requires horizontal coil rack storage, occupying 1.5 times the space of flat sheets.

• Minimum order quantity: PPGI accepts orders starting from 5 tons, while PPGL typically requires orders of 20 tons or more.

• It is recommended to choose PPGL coils for bulk purchases, and prioritize PPGI steel sheets for small-batch custom orders.

Professional material selection advice and solutions

Maxwell Steel, with 15 years of experience in steel export, recommends selecting based on the end-use application: PPGI is preferred for surface decorations such as building curtain walls and elevator cars; PPGL is recommended for continuously molded products such as ventilation ducts and cable trays. We can provide:

• Free Material Certificate (MTC) and RoHS test report provided.

• Customized coating weight and color (Pantone color chart matching) supported.

• Port DDP/DAP delivery service, resolving customs clearance issues.

Contact our technical consultant now (+86 13584181580) to obtain a customized PPGI/PPGL quotation and processing guide.