f you are sourcing color coated steel coils, you have probably come across both PPGI and PPGL. They look almost identical. Same paint systems, same color options, same basic application as roofing and cladding material. But the substrate underneath is different, and that difference matters more than most buyers realize.

Pick PPGI for the wrong environment and it will corrode faster than it should. Pick PPGL when you did not need it and you are paying extra for performance you will never use. This article walks through the differences so you can make the right call.

What Is the Difference? The Substrate

The only real difference between PPGI and PPGL is the metallic coating on the base steel before painting.

Key Difference 1: Corrosion Resistance

This is the main reason buyers choose PPGL over PPGI. The aluminum in the galvalume coating forms a stable oxide barrier that resists atmospheric corrosion significantly better than pure zinc.

In standardized salt spray testing (ASTM B117), PPGL lasts 2-4 times longer before showing red rust compared to PPGI with an equivalent coating mass. In real-world coastal exposure, PPGL roofing panels typically last 20-25 years versus 10-15 years for standard PPGI.

However, there is a trade-off. PPGI provides better cathodic protection at cut edges and scratches. If your panels will be cut to length on site with exposed edges, and you are in a moderate environment, PPGI's sacrificial protection is actually an advantage.

Key Difference 2: Heat Reflectivity

PPGL's aluminum-rich surface reflects more solar radiation than PPGI. This makes it a popular choice for cool roof applications in tropical and subtropical climates. Some studies show 5-10°C lower peak roof temperatures with PPGL compared to PPGI under the same conditions.

For warehouses and industrial buildings without air conditioning, this can make a real difference in internal temperature and worker comfort. It is also becoming a factor in green building certifications like LEED.

Key Difference 3: Formability and Fabrication

PPGI is generally easier to form. The pure zinc coating is more ductile and forgiving during bending, punching, and roll forming. PPGI is a safe choice for complex profiles and deep drawn parts.

PPGL's Al-Zn coating is slightly harder and more brittle. On very tight bends, micro-cracks can form if the material quality is not up to standard. That said, high-quality PPGL with a good T-bend rating (1T or better) handles standard roll forming without issues.

If your project involves lots of tight bends or deep drawing, PPGI is the safer bet. If it is mostly standard roll-formed profiles, PPGL works just fine.

Key Difference 4: Cost

PPGL typically costs 5-10% more than PPGI with the same paint system and steel grade. The premium comes from the more expensive aluminum-zinc coating materials.

For a large roofing project covering 10,000 m², this premium can add up. Many buyers in cost-sensitive markets default to PPGI for standard inland projects and spec PPGL only where the environment justifies it.

Key Difference 5: When to Choose Each One

What to Check Before You Buy

Whether you choose PPGI or PPGL, here is what to verify with your supplier.

• Coating mass report. Z60-Z275 for PPGI, AZ70-AZ185 for PPGL. Make sure the report matches the contract.
• T-bend test. 0T or 1T is ideal. This tells you the paint will not crack during forming.
• Paint system confirmation. PE, SMP, HDP, or PVDF. Environmental conditions determine the right choice.
• MTC (Mill Test Certificate). Chemical composition, mechanical properties, and coating data from the actual production batch.
• Third-party inspection. A supplier that allows SGS or BV inspection is a supplier with nothing to hide.

One more thing. Do not mix PPGI and PPGL on the same roof. Dissimilar metals can cause galvanic corrosion where they touch. Stick with one substrate for the entire project.

About CAMELSTEEL

We supply both PPGI and PPGL produced to EN 10346 and JIS G3323 standards. With 25+ years in the steel business and 600,000+ tons annual capacity, we can match the right substrate to your project conditions.

• PPGI range: DX51D-DX53D, Z60-Z275, PE/SMP/HDP/PVDF paint
• PPGL range: AZ70-AZ185, same paint system options
• Colors: Full RAL range, custom colors available