How to Choose Color Coated Steel Coil (PPGI) for Roofing and Wall Cladding
Choose the right color coated steel coil (PPGI) for roofing and cladding: substrate grade, zinc coating, paint system, RAL colour and thickness, plus what to send for a fast quote.
Choosing a color coated steel coil (PPGI) comes down to five decisions: the steel substrate and grade, the zinc coating weight, the paint system, the front and back coating thickness, and the coil dimensions. Get them right and the coil keeps its colour and resists corrosion for years. Get one wrong and you can see chalking, peeling or edge rust long before the service life you planned for.
This guide explains what each factor does, the ranges we supply from our mill in Anyang, Henan, and the exact information to send us so you receive a quotation you can compare line by line.
What is a color coated steel coil (PPGI)?
A color coated steel coil - also written colour coated steel coil, prepainted galvanized steel coil or PPGI (pre-painted galvanized iron) - starts as a galvanized steel substrate. A continuous coating line then applies a primer and one or more top coats, cures them in an oven and rewinds the coil. The zinc layer protects the steel; the paint layer protects the zinc and gives the coil its colour and surface finish.
Because the coating is applied before the coil is cut, slit or roll-formed, PPGI arrives ready to turn into roofing sheets, wall panels, sandwich panels and appliance parts with no separate painting step. That is why it is called 彩钢卷 in Chinese and "prepainted coil" in most export markets.
PPGI or PPGL - which one do you need?
PPGI uses a hot-dip galvanized substrate (zinc coating). PPGL uses a galvalume substrate (aluminium-zinc coating). PPGL has better heat reflection and suits high-temperature and some coastal applications; PPGI is the more economical and more widely used choice for general roofing and wall cladding. The painting process is the same for both.
The five factors to compare before you buy
1. Steel substrate and grade
The grade describes the yield strength and forming behaviour of the base steel. Commercial drawing grades such as DX51D and DX52D are the workhorses for roofing and cladding. Structural grades run from S250GD up to S550GD: the higher the number, the higher the yield strength, which helps with long spans and load-bearing profiles. Higher strength also means less formability, so do not over-specify if the coil will be profiled or bent heavily.
We supply DX51D, DX52D, DX53D, DX54D, S250GD, S280GD, S320GD, S350GD and S550GD, produced to AISI, ASTM, DIN, JIS, GB or EN standards.
2. Zinc coating weight
The zinc coating is normally written in grams per square metre (g/m²) or as a Z value. More zinc means longer corrosion protection, and on a roof or façade it is the single biggest driver of service life.
As a rule of thumb: indoor and dry inland use needs less zinc; general outdoor roofing and cladding needs a mid-range coating; coastal, humid, industrial or chemical environments need the heaviest coating you can justify. The galvanized substrate we coat is the same hot-dip galvanized steel we supply on its own, with zinc coatings from 30 to 275 g/m². Tell us where the coil will be installed and we will recommend a starting point.
3. Paint system: PE, SMP, HDP or PVDF
The paint system decides how well the colour survives sun, rain and pollution.
- PE (polyester) - the most economical option; good for indoor parts, general roofing and shorter-life projects.
- SMP (silicone-modified polyester) - better UV resistance and colour retention than standard polyester; a common upgrade for outdoor roofing.
- HDP (high-durability polyester) - formulated for façades and long-life buildings where colour consistency matters.
- PVDF (fluorocarbon) - the best colour and gloss retention of the four; used on demanding architectural and coastal projects.
We coat with PE, SMP, HDP or PVDF. If your project has an architectural specification or a colour warranty, quote the paint system in your enquiry - a RAL number on its own does not define it.
4. Coating thickness, front and back
Coating thickness is quoted separately for the top (front) and reverse (back) face, in micrometres. We supply 18-35 µm on the front and 10-35 µm on the back. A thicker front coat gives more UV and weather protection; the back coat protects the underside of a roofing sheet, which is the side most buyers forget and the side that rusts first in a humid building.
5. Thickness, width and coil size
Our color coated steel coil is produced from 0.3 mm to 2.0 mm thick and 600 mm to 1500 mm wide, with a cutting service from 3 mm to 1500 mm for slit coil and sheet. Coil inner diameter, outer diameter and coil weight are agreed with the order so the coil fits your uncoiler and your crane capacity.
Matching the coil to the application
Before comparing prices, write down the application and the environment. Those two answers narrow the specification faster than anything else:
- Roofing and wall cladding, inland - DX51D or S250GD, mid-range zinc, PE or SMP.
- Coastal or heavy-rain roofing - heavier zinc coating, PVDF or HDP, and close attention to cut edges and fasteners.
- Architectural façades - SMP, HDP or PVDF, consistent colour between batches, tighter thickness tolerance.
- Sandwich panels - flatness, coating adhesion and uniform colour matter more than maximum strength.
- Appliances and indoor parts - thin PE-coated coil with a clean surface finish; the zinc requirement is lower.
Common mistakes we see in PPGI enquiries
- Giving a RAL colour but not the paint system, so suppliers quote PE against a PVDF specification.
- Forgetting the back coating, then finding the underside of the roof rusts first.
- Choosing the zinc coating on price alone for a coastal or industrial site.
- Specifying a structural grade for a profile that needs deep forming.
- Leaving coil weight and inner diameter out, which delays the quotation.
Frequently asked questions
What does PPGI stand for?
Pre-painted galvanized iron. In practice it means a color coated steel coil with a galvanized substrate: zinc coating underneath, paint on top.
Is color coated steel coil the same as 彩钢卷?
Yes. 彩钢卷 is the Chinese term for a color coated steel coil. If a supplier, drawing or purchase order uses that term, it means a prepainted galvanized or galvalume coil.
How long will a PPGI roof last?
Service life depends on the zinc coating weight, the paint system, the atmosphere and how the sheets are cut and fixed. We will not promise a fixed number of years without knowing the site, so tell us the location and environment and we will propose a specification to match. Test certificates and third-party testing such as SGS can be arranged with the order.
Can you match a specific RAL colour?
Yes. Send the RAL code, the paint system and the gloss level you expect, and confirm whether the colour has to match an existing building or a previous delivery.
What is the difference between PPGI and a galvanized steel coil?
PPGI has paint on top of the zinc coating. A galvanized steel coil (GI) has the zinc coating only and keeps its natural silver-grey surface. If appearance, colour and a paint warranty matter, choose PPGI; if the coil will be painted later or the finish is not important, galvanized coil is usually more economical. The specification side is covered in our galvanized steel coil buying guide.
What quantity do you require, and how fast can you quote?
It depends on grade, colour and coil size. Send your required quantity in tonnes or kilograms and we will confirm availability and the delivery schedule with the quotation. Most enquiries receive a detailed quotation within 24 hours by email, WhatsApp or WeChat.
What to send us for a fast, accurate quotation
- Application and environment (roofing, cladding or appliance; coastal, inland or industrial).
- Steel grade, or the mechanical properties you need.
- Thickness (mm) and width (mm), plus slit or cut-to-length requirements.
- Zinc coating weight, and whether the substrate is galvanized or galvalume.
- Paint system (PE, SMP, HDP or PVDF) and front and back coating thickness.
- RAL colour, gloss level, and whether the colour must match an existing panel.
- Quantity, coil inner diameter, coil weight and destination port.
Next step
Send these details to Anyang Yehui Steel Company and we will come back with a specification you can compare line by line:
- Browse the full color coated steel products range.
- See the specification of our Color Coated PPGI Coil and UV Resistant PPGI Steel Sheet.
- Email joy@ayyehui.com, message WhatsApp or WeChat on +86 17337296907, or send an enquiry with your specification.
