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Choosing the Right Corrosion Protection: GI, Galvalume, or ZAM?

RAD PREFABS — Technical Insight Series

Choosing the Right Corrosion Protection:
GI, Galvalume, or ZAM?

A clear, objective comparison for steel structure projects

When it comes to steel structures, corrosion protection is not a one-size-fits-all decision. The choice of coating directly impacts your project's durability, maintenance costs, and long-term performance.

At RAD PREFABS, we often guide clients through three widely used options:

Hot-Dip Galvanised (GI) · Aluminium-Zinc Alloy Coated (Galvalume/GL) · Zinc-Aluminium-Magnesium Coated (ZAM)

To help you make an informed decision, we have prepared a clear, objective comparison based on coating composition, protection mechanisms, service life in various environments, and cost-effectiveness.

— · — · — · —

1 Coating Composition & Protection Mechanisms

Aspect	GI	Galvalume (GL)	ZAM
Typical Composition	Pure zinc (≥99.9% Zn, trace Al)	55% Al + 43.4% Zn + 1.6% Si	84.5–91% Zn + 5–6% Al + 3% Mg
Protection Mechanism	Sacrificial anode (zinc) + physical barrier	Al oxide barrier + Zn cathodic protection	Zn cathodic + Al passivation + Mg self-healing
Cut-Edge Protection	Poor – edges rust easily, require secondary coating	Moderate – oxide layer limits Zn flow	Excellent – Mg ions migrate to edges, forming dense protective film

💡 Key takeaway: ZAM's unique self-healing edge protection is a game-changer, eliminating costly post-fabrication repairs.

— · — · — · —

2 Corrosion Performance & Service Life

Typical values for reference

Service Environment	GI	Galvalume	ZAM
General Atmospheric	10–15 years	>20 years	20–30 years
General Building / Structural	20–30 years (AS/NZS compliant)	25 years (AZ150 warranty)	25–30 years
Marine / High Salt Spray	5–10 years	15–50 years (varies by coast distance)	>25 years
C5 High-Corrosion Environment	Needs 140μm coating for 25 years	—	25 years with heavy ZAM coating
Extreme Aggressive Conditions	Short life; frequent maintenance	25–50 years	>50 years

Relative Corrosion Resistance (vs. GI as baseline):

GI1×

Galvalume2–6×

ZAM3–20×

— · — · — · —

3 Key Properties at a Glance

Property	GI	Galvalume	ZAM
Self-Healing at Cut Edges	No	No	Yes – Mg ion migration
Alkali Resistance	Good	Weak	Good
Acid Resistance	Moderate	Excellent	Excellent
Coating Hardness	Soft (~150 HV)	—	Harder (200–300 HV)
Fabrication Convenience	Needs post-coating repair after cutting/welding	Poor weldability	Cut/drill directly; no edge repair needed
Cost	Lowest	Medium	Highest

— · — · — · —

4 Which One Should You Choose?

GI — The Economical Workhorse

Best for: General building structures, normal atmospheric conditions, cost-sensitive projects

✓ Advantages: Mature technology, lowest cost; can achieve >50 years in many Australian inland areas

✗ Limitations: Edge treatment required; limited life in severe corrosive environments

Galvalume — The Heat & Acid Specialist

Best for: Roofing, high-temperature equipment, general industrial areas

✓ Advantages: Excellent heat resistance (up to 315°C), superior acid resistance, high light reflectivity

✗ Limitations: Weak alkali resistance; only moderate edge protection

ZAM — The Premium Solution

Best for: Coastal projects, solar mounting, marine engineering, agricultural facilities — any high-corrosion setting

✓ Advantages: Best overall corrosion resistance, self-healing edges, abrasion-resistant

✗ Limitations: Highest initial cost

— · — · — · —

5 Summary — Quick Comparison

Dimension	GI	Galvalume	ZAM
Corrosion Performance	★★☆	★★★☆	★★★★★
Edge Protection	★☆	★★☆	★★★★★
Overall Service Life	10–30 years	20–50 years	25–50+ years
Cost	Low	Medium	High
Recommended Application	General construction	Roofing / high-temp	Coastal / extreme

— · — · — · —

Final Recommendation

GI remains the economical, proven workhorse for standard applications where environmental corrosivity is low.

Galvalume excels in heat resistance and acidic environments, making it the ideal choice for roofing, cladding, and industrial panels.

ZAM offers the highest corrosion resistance and unique cut-edge self-healing — the premium solution for demanding coastal, marine, or harsh industrial projects where long-term durability is critical.

We recommend that the final selection be based on a thorough assessment of the site's corrosivity category (per ISO 12944), the required design life, and the overall project budget.

— · — · — · —

Need Expert Guidance?

At RAD PREFABS, we don't just supply steel — we provide tailored corrosion-protection strategies. Our technical team can conduct a site-specific evaluation, recommend the optimal coating weight, and supply full test reports to support your decision.

RAD PREFABS

A Brand of Leader Building Materials Co., Ltd.

Engineered for Durability. Built for Life.

Follow our Technical Insight series for more in-depth material comparisons and design guidance

Pub Time : 2026-07-15 19:00:03 >> News list

Contact Details

FOSHAN RAD PREFABS COMPANY LIMITED

Contact Person: Ms. Evana Yim

Tel: +8613924859314

company news about Choosing the Right Corrosion Protection: GI, Galvalume, or ZAM?

Expandable Container House

Modern Prefab Houses

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Luxury Prefab House

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FR-NEW ENERGY CHARGING PILE

Prefabricated mobile Single Toilet

Prefabricated Mobile Multiplayer Toilet

Outdoor lighting

Outdoor lighting

Furniture

Choosing the Right Corrosion Protection:
GI, Galvalume, or ZAM?

1 Coating Composition & Protection Mechanisms

2 Corrosion Performance & Service Life

3 Key Properties at a Glance

4 Which One Should You Choose?

5 Summary — Quick Comparison

Final Recommendation

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