Galvalume and galvanized are the two most common metallic coatings used on steel coil for roofing and construction, and choosing correctly has a direct impact on service life and cost. This guide from ChinaCNU Steel — a China-based galvalume and galvanized steel coil manufacturer — explains the difference and helps you decide.
What Is Galvanized Steel?
Galvanized (GI) steel is hot-dip coated with pure zinc (typically Z40–Z275, i.e. 40–275 g/m²). The zinc provides sacrificial, self-healing corrosion protection and the coating is easy to form, weld and paint. It is the economical, all-round choice.
What Is Galvalume (Aluzinc) Steel?
Galvalume — also called aluzinc or GL — is hot-dip coated with an alloy of about 55% aluminium, 43.4% zinc and 1.6% silicon (AZ50–AZ150). The aluminium forms a stable barrier layer while the zinc still offers sacrificial protection at cut edges, giving substantially longer life in most environments.
Galvalume vs Galvanized: Side-by-Side Comparison
| Property | Galvanized (GI) | Galvalume (AZ / GL) |
|---|---|---|
| Coating | Pure zinc (Z40–Z275) | 55% Al + 43.4% Zn + 1.6% Si (AZ50–AZ150) |
| Corrosion resistance | Good | 2–4× better at equal coating weight |
| Typical service life | 10–20 years | 25+ years |
| Cut-edge protection | Excellent (high zinc) | Good |
| Formability / weldability | Excellent | Good |
| Heat reflectivity | Lower | Higher (aluminium) |
| Cost | Lower | Slightly higher |
| Best for | Budget projects, heavy forming, ducts, framing | Long-life roofing, coastal & high-heat areas |
Which Should You Choose?
Choose galvanized when budget is the priority, when the part will be heavily bent or welded (ductwork, framing, agriculture), or where the environment is mild. Choose galvalume for long-life metal roofing, hot or coastal climates, and solar mounting where extended corrosion resistance justifies the small price premium. For coloured roofing, both can be pre-painted — galvanized becomes PPGI and galvalume becomes PPGL; see our PPGI coil page.
Frequently Asked Questions
Is galvalume better than galvanized?
For corrosion resistance and lifespan, yes — galvalume typically lasts 2–4× longer at the same coating weight. Galvanized is better for heavy forming, welding and tight budgets.
Can galvalume be welded?
It can, but the aluminium content makes it slightly harder to weld than galvanized; mechanical fixing is often preferred.
Which is cheaper, galvanized or galvalume?
Galvanized is usually a little cheaper per ton. The gap is small and galvalume’s longer life often gives a lower lifetime cost for roofing.
Do you supply both?
Yes. ChinaCNU manufactures both GI / galvanized coil and aluzinc / galvalume coil. Send your spec and tonnage for a 24-hour FOB Tianjin or CFR quote.
Need help choosing? Tell us your application, environment and budget and our engineers will recommend the right coating and coating weight, then quote within 24 hours.