For inland roofing the answer is usually price. For coastal projects, the base coating under the paint decides how long the roof lasts. Here is the honest comparison between PPGI (zinc base) and PPGL (aluzinc base).
Head to Head
| Factor | PPGI (Z base) | PPGL (AZ base) |
|---|---|---|
| Base coating | Zinc Z80-Z180 | Aluzinc AZ50-AZ150 (55% Al) |
| Flat-surface corrosion | Good | Better — 2-4x in salt spray tests |
| Cut-edge protection | Better (zinc is sacrificial) | Weaker on thick sheet edges |
| Heat reflection | Standard | Better (aluminium content) |
| Price | base | +3-6% |
Our Recommendation by Market
- Within ~5 km of coast, high humidity: PPGL with SMP or PVDF paint.
- Inland, price-driven markets: PPGI with PE paint remains the volume seller.
- High UV (Middle East, Andes): either base, but upgrade the paint to SMP minimum — UV kills PE topcoats before the base corrodes.
FAQ
Why does PPGL sometimes fail at cut edges?
The aluminium-rich coating is less sacrificial than pure zinc, so exposed edges on thicker sheets corrode first. On thin roofing gauge (0.30-0.50mm) this is rarely a practical problem.
Can you supply both in one order?
Related Products from ChinaCNU Steel
Yes — mixed PPGI/PPGL containers are common, MOQ 25 tons total. See our galvalume vs galvanized guide for the unpainted comparison.