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PPGI Coil: Purchase Guide and Knowledge

PPGI stands for Pre-Painted Galvanized Iron, a type of steel product that has undergone a series of processes to enhance its durability and aesthetic appeal.

PPGI coils are essentially galvanized steel sheets that are coated with a layer of paint or other protective coatings.

PPGI Coil: Purchase Guide and Knowledge 1

This pre-painting process involves cleaning, treating, and painting the steel before it is rolled into coils.

The result is a product that combines the strength and corrosion resistance of galvanized steel with the added benefits of a protective and decorative paint layer.

Profile Structure of PPGI Coils

PPGI Coil: Purchase Guide and Knowledge 2

PPGI coil provides long-lasting and durable performance over the years. The method gives uniform cleaning, coating, and pre-treatment on the metal surface. The highly controlled coating process gives the metal coil several synergistic layers that include the following:

  • Topcoat
  • primer
  • Pre-treatment
  • Metallic Coating
  • Metal


Core Components and Materials


  1. Galvanized Iron Substrate


   – The base material for PPGI coils is galvanized iron, which is steel that has been coated with a layer of zinc to protect it from corrosion. The galvanized coating acts as a sacrificial layer, preventing rust and extending the life of the steel. This substrate provides the structural integrity and durability required for various applications.


  1. Pre-Painted Layers


   – Primer Layer:  The first layer of paint applied to the galvanized iron is the primer. This layer enhances the adhesion of the topcoat and provides additional corrosion resistance. Primers are usually made from epoxy or polyester resins, which offer excellent bonding properties.

   – Topcoat Layer: The topcoat is the final layer of paint that provides the desired color and finish. This layer is not only decorative but also adds an extra level of protection against environmental factors such as UV radiation, moisture, and chemicals. The topcoat can be made from various types of paints, including polyester, polyurethane, and PVDF (polyvinylidene fluoride), each offering different levels of durability and aesthetic qualities.

   – Optional Backing Coat: In some cases, a backing coat is applied to the reverse side of the coil to provide additional protection and improve the overall performance of the PPGI coil.


The Difference Between PPGI Coil and PPGL Coil

PPGI Coil: Purchase Guide and Knowledge 3


Here’s a comparison table highlighting the differences between PPGI (Pre-Painted Galvanized Iron) Coil and PPGL (Pre-Painted Galvalume) Coil:


FeaturePPGI CoilPPGL Coil
Base MaterialGalvanized Iron (GI)Galvalume (GL), which is a combination of zinc, aluminum, and silicon
Corrosion ResistanceGood, due to the zinc coatingExcellent, due to the combination of zinc and aluminum
DurabilityDurable, but less so compared to PPGLMore durable due to better corrosion resistance
Coating CompositionZinc coatingZinc-Aluminum coating (typically 55% aluminum, 43.4% zinc, 1.6% silicon)
AppearanceSmooth and shiny surfaceSmoother and more reflective surface due to aluminum
WeightHeavier than PPGLLighter due to the aluminum content
Heat ResistanceModerateBetter heat resistance because of aluminum
CostGenerally lowerGenerally higher due to better properties
ApplicationsConstruction, automotive, appliances, etc.Construction, especially in harsh environments, roofing, and cladding
LifespanShorter compared to PPGLLonger lifespan due to superior corrosion resistance


Purchase Guide

Choosing the right PPGI Coil material is related to the purpose and environment. PPGI Coil consists of galvanized steel coils and different paints. Here’s how to choose.


Choose galvanized steel sheet


  • Grade


The galvanized steel coil is the substrate of PPGI Coil, the first choice is to confirm the steel grade of galvanized coil, which is related to the use of PPGI Coil.

Choose commercial steel and structural steel for construction. Commercial steel is a cold forming low-carbon steel for bending and prfiling quality.

It is usually processed into corrugated roof tiles by cold forming machines. Structural steel is used for building facades and lightweight steel structures with a focus on yield strength.

Common commercial steel grades are DX51D to EN 10346 and CS type A to ASTM A653. Structural steel is S250GD, S280GD, S350GD, S550GD, etc. according to EN 10346 standard, and the number 550 means the yield strength is 550Mpa.

In addition to its application in the construction field, PPGI Coil can also be used as the shell of home appliances. For example, the shell of lamps needs DX52D material with drawing quality.


  • Zinc layer weight


The coating mass of galvanized sheet for construction is usually 30-275 g/m2. Z275 galvanized coil substrates are used in highly corrosive environments such as coastal areas, and Z100 galvanized coil substrates can be used in housing construction in ordinary environments.


Choose Paint


Polyester is PPGI Coil’s most widely used paint and it can provide an economical product. Has low resistance to the effects of UV rays and low corrosion resistance to chemicals. Suitable for areas with low environmental corrosion.

SMP has excellent scratch resistance and excellent adhesion and is easier to chalk and fade under ultraviolet light than PVDF.

The main properties of High durability polyester(HDP) are strong weather resistance and strong corrosion resistance. It is mainly used in areas with long sunshine times, high dryness, large temperature difference between day and night, and strong humidity.

PVDF is relatively strong in anti-ultraviolet rays, not easy to decompose in sunlight, improves anti-fading and chalking ability, and maintains color luster for a long time. PVDF has strong corrosion resistance and is suitable for use in coastal areas.

Durability: PVDF >High durability polyester(HDP)>Silicon modified polyester(SMP)>Polyester(PE)


Select Coating Structure

PPGI Coil: Purchase Guide and Knowledge 4

PPGI Coil has 2 coating structures, 2/1 and 2/2. 2/2 means top finish coating and back finish coating, and 2/1 means no back finish coating.

Sandwich panels are suitable for 2/1 structures, and high-durability roofs are suitable for 2/2 structures.


PPGI Coil Manufacturing Process


The manufacturing process of PPGI coils involves several key steps:


  • Substrate Preparation: The process begins with the preparation of the steel substrate, which is usually cold-rolled steel. This substrate is cleaned and treated to ensure proper adhesion of subsequent layers.


  • Galvanizing: The cleaned steel substrate is then coated with a layer of zinc to provide corrosion resistance. This can be done through different methods such as hot-dip galvanizing or electro-galvanizing. The zinc coating protects the steel from rust and extends its lifespan.


  • Chemical Treatment: After galvanizing, the steel undergoes a chemical treatment to enhance the adhesion of the paint layers. This step often involves the application of a chromate or phosphate coating.


  • Primer Coating: A primer coating is applied to the treated steel. The primer serves as a base layer that improves the adhesion of the topcoat and provides additional corrosion resistance. It is usually applied using a roll-coating process and then cured in an oven.


  • Top Coating: Once the primer has cured, the topcoat is applied. This coat provides the desired color and finish to the PPGI coil. The topcoat is also applied using a roll-coating process and then cured in an oven. Various types of paints can be used, including polyester, silicon-modified polyester, polyvinylidene fluoride (PVDF), and epoxy.


  • Quality Control: Throughout the manufacturing process, rigorous quality control measures are implemented to ensure that the PPGI coils meet specified standards. This includes checking the thickness of the coatings, adhesion, color consistency, and overall appearance.


  • Coil Winding: After the topcoat has cured and passed quality control checks, the steel is wound into coils. These coils are then packaged and prepared for shipment to customers.


Benefits of Using PPGI Coils


Pre-painted galvanized iron (PPGI) coils offer numerous advantages across various applications. Here are some of the key benefits:


  1. Durability and Long Lifespan: PPGI coils are known for their robust nature, providing long-lasting performance even in harsh environmental conditions. The galvanization process enhances their resistance to wear and tear, ensuring a prolonged service life.


  1. Aesthetic Versatility: 

   – Variety of Colors and Finishes: PPGI coils are available in a wide range of colors and finishes, allowing for versatile aesthetic applications. This makes them ideal for architectural and design projects where appearance is crucial.


  1. Corrosion Resistance: The galvanization process provides a protective coating that helps prevent rust and corrosion, making PPGI coils suitable for use in environments prone to moisture and other corrosive elements.


  1. Cost-effectiveness: PPGI coils offer an economical solution due to their durability and low maintenance requirements. Their long lifespan and resistance to damage reduce the need for frequent replacements, leading to cost savings over time.


  1. Environmental Benefits:

   – Recyclability: PPGI coils are recyclable, making them an environmentally friendly choice. The materials can be reprocessed and reused, reducing waste and conserving natural resources.

   – Reduced Need for Maintenance: The durability and corrosion resistance of PPGI coils mean that they require less frequent maintenance and replacements, which in turn reduces the environmental impact associated with manufacturing and transportation.



Overall, PPGI coils are a versatile and sustainable option for a wide range of applications, combining aesthetic appeal with practical benefits.

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