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Plain Roof Steel

Plain Roof Steel

The prepainted steel sheet in coil is a product obtained by subjecting a hot-dipped galvanized steel sheet, an galvalume steel sheet, or an aluminum sheet to a surface chemical treatment (coating) , followed by baking and curing.

  • The total thickness of the pre-panted galvanized steel coil is composed of the base steel – coating -primer – top paint – protective layer thickness. The top paint thickness is 10-25μm, and the back paint thickness is 5-20μm. The thinner the base steel thickness, the higher the price of the ppgi steel coil, because the processing cost becomes higher.
  • Usually the paint coating material is polyester (PE) and the color of the back paint is white grey. The color can be customized according to the RAL color card or customer samples. Special patterns can be made, such as wood grain, flower print, camouflage, brick.
  1. PPGI also known as prepainted galvanized steel coil and color coated steel coil, with a hot dip zinc coated steel sheet substrate.
  2. PPGL also known as prepainted galvalume steel coil, with a galvalume steel sheet as a substrate.

The decoiler machine unwinding, leveling, fixed length, cut the prepainted galvanized steel coil into a flat PPGI sheet of the required length and width and is processed into a PPGI&PPGL roofing sheet of various styles by a roll forming machine, such as corrugated steel sheet, wave tile, roman longtile profile.

Pre-painted Steel Products


The matt PPGI has big wrinkle PPGI and small wrinkle PPGI. The paint coating thickness is 20μm-45μm, which is used for roofing sheet which is not easy to discolor and has a longer service life.

Polyester color coated sheet in coil

It is coated on a metal sheet with a polyester coating and baked at a high temperature.
Good adhesion, formability, outdoor durability, chemical resistance
Roofing sheet of Industrial workhouse, warehouse.

PVDF prepainted steel sheet in coil

It is coated on a metal plate with PVDF paint and baked at high temperature.
High durability, high flexibility, impact resistance, still maintain good color and luster for 15 years outdoors
For buildings with high corrosion resistance

Brick pre-painted steel sheet in coil

The brick pattern is printed on a galvanized or galvalume steel sheet.
Outdoor decoration, interior wall

Marble color coated coil

The marble pattern is printed on a galvanized or galvalume steel sheet.
Indoor, outdoor wall

Matt Colour coated coil

Attached to a galvanized or galvalume steel sheet with a high performance polyester coating containing abrasive particles.
The surface of the coating is ultra-low gloss, close to the natural matte feel
High-rise buildings, villas, roofing tiles

Camouflage color steel coil

Print camouflage patterns on galvanized or aluzinc steel sheets.
Indoor, outdoor wall

Wooden design prepainted steel coil

Print wood grain patterns on galvanized or aluzinc steel sheets.
House door, garage door

HDP Colour coated steel coil

Attached to galvanized or galvalume steel sheet with high performance polyester coatings.
UV resistant, better durability, between polyester and PVDF
For buildings with high corrosion resistance


PPGI Coil Production Process Flow Chart


Unrolling → Stitching machine → Entrance loop → Pretreatment → Initial coating → Bake → Cool down → Fine coating → Bake → Embossed film → Export loop → Inspection station → Cut → Coiling

In the above process, if the cleaning degreasing process is not handled well, the adhesion of the primer of the color coated plate to the galvanized sheet is not good, and it is easy to cause the top coat of the color coated steel coil to fall off during the press forming process.

PPGI & PPGL Sheet Coating Layer

  • Top (Finish) Coating (PE/HDP/PVDF, etc.)
  • Primer Coating
  • Pre Treatment (Chromate Coating)
  • Plating Layer (Zn, AL, 55%AL+Zn)
  • Base Metal (Cold Rolled Steel Sheet)
  • Plating Layer (Zn, AL, 55%AL+Zn, Sn, Cr etc.)
  • Pre Treatment (Chromate Coating)
  • Functional Painting (Epoxy, Polyester )

PPGI Quality Control

PPGI & PPGL steel quality control according to the following:

  • coating thickness test
  • color difference test
  • gloss test
  • T bend
  • tensile test
  • impact test

PPGI paint coating

Coating Primer Top paint coating Service life (years)
1) Epoxy primer, good adhesion, water resistance, alkali resistance, chemical corrosion resistance, poor single toughness.
2) Polyester primer, good adhesion, good flexibility, sensitive to humid environment, chemical resistance is not as good as epoxy primer.
3) Acrylic primer, good adhesion, good toughness and high pretreatment requirements.
4) polyurethane primer, chemical resistance, abrasion resistance, durability, toughness
1) Polyester resin, good adhesion, molding and outdoor durability. 8-10
2) Silicon Modified Polyester (SMP) 10-15
3) High weather resistant polyester (HDP) 12-15
4) Polyvinyl fluoride (PVC) 12-15
5) Polyvinylidene fluoride/fluorocarbon (PVDF) It has good formability and color retention, good outdoor durability and powder resistance, solvent resistance, limited color and high price. 12-20

PPGI Steel Sheet Applications

Color coated steel coil/sheet (PPGI & PPGL) is widely used in:

  • Building
  • Roofing
  • Transport
  • Home Appliances, such as the side door plate of refrigerators, shell of DVDs, air conditioners and washing machines.
  • Solar Energy
  • Furniture


Material CGCC, DX51D, Q195,Q235
Zinc 20-120g
Thickness 0.13-0.8mm
Width 600-1250 mm
Color all RAL color, as Client's request
Paint top paint- 10-30mic  back paint-5-25mic
T bend  
Pencil Hardness >2H
Coil ID 508/610mm
Coil Weight 3-8tons
Surface glossy and matt
Glossy 30%-90%
Package Standard export package
Hardness Soft, hard, full hard
HS Code 721070