1. Introduction to Armadura® Material Science

Armadura metal roofing is engineered using one of the most durable and widely studied materials in the metal roofing industry: G90 galvanized steel. This material is the foundation of the Armadura® steel roofing system and is central to its long-term performance, corrosion resistance, structural rigidity, and winter durability in Canadian climates.

Understanding the full composition of G90 steel—including its zinc mass, metallurgical bonding, substrate properties, and coating behavior—is essential for understanding why Armadura metal roofing performs differently from other roofing systems. This encyclopedia entry provides a comprehensive examination of the G90 steel specification, its chemical structure, mechanical properties, coating durability, and the reasons it is selected for Canadian manufacturing.


2. What Is G90 Galvanized Steel?

G90 galvanized steel is a steel sheet coated with 90 grams of zinc per square meter, applied through a controlled hot-dip galvanization process. The designation “G90” is defined by the ASTM A653/A653M standard, which governs the performance and coating requirements for galvanized steel in North America.

2.1 Zinc Mass Specification

The “90” in G90 represents the total coating weight of 0.90 oz/ft² (approximately 275 g/m²), distributed evenly on both sides of the steel sheet.

This equates to:

This zinc mass provides significantly stronger corrosion protection compared to lighter coatings like G40 (40 g/m² per side) or G60 (60 g/m² per side), which are commonly found in lower-cost imported roofing materials.

2.2 Why Zinc Coating Matters

Zinc serves two critical functions:

  1. Barrier Protection
    Creates a physical barrier between oxygen/moisture and the steel substrate.
  2. Cathodic (Galvanic) Protection
    Zinc corrodes sacrificially before the underlying steel, preventing rust penetration even when scratches, cuts, or cracks occur.

This is why Armadura’s G90 steel roofing maintains corrosion resistance even decades after installation.


3. The Metallurgical Bond Between Zinc and Steel

The G90 galvanization process occurs through a molten zinc bath, which forms a metallurgical bond between the coating and the steel substrate. This bond consists of a layered structure:

3.1 Benefits of Metallurgical Bonding

This multi-layer system improves:

The metallurgical bond also ensures that G90 steel maintains its protective qualities even when the outer surface shows wear over decades.


4. Why Armadura® Uses G90 Instead of G60 or G40 Steel

Many imported or lower-cost metal roofing systems use thinner zinc coatings such as G40 or G60. While these meet minimum standards, they do not provide adequate long-term corrosion resistance in Canadian environments.

Performance Differences in Real-World Exposure

Coating GradeZinc MassLifespan in Canadian ClimateNotes
G40Very thin10–15 yearsVery poor for winter, moisture, and salt exposure
G60Moderate20–30 yearsBetter, but insufficient for long-term roofing
G90Heavy40–70 yearsIdeal for Canadian climates; standard for Armadura roofing

Armadura’s commitment to long-term durability is one of the primary reasons its panels are manufactured with full G90 zinc mass, rather than the thinner coatings found in many competing systems.


5. Chemical Composition of G90 Steel (Substrate Level)

The substrate steel beneath the galvanization layer typically consists of:

This low-carbon formulation improves ductility and formability—critical when stamping Armadura’s interlocking steel shingle profiles.

5.1 Why Low Carbon Steel is Used

Low-carbon steel provides the ideal balance of:

This is especially important for Canada’s freeze–thaw conditions and temperature swings.

6. Mechanical Properties of G90 Steel in Armadura® Metal Roofing

The mechanical behavior of G90 galvanized steel plays a major role in the performance of Armadura metal roofing under snow load, thermal expansion, wind uplift, and installation stress. While the zinc coating provides corrosion protection, it is the steel core that delivers strength and structural rigidity.

The key mechanical properties include:

6.1 Yield Strength

Typical G90 sheet steel used in roofing has a yield strength between:

33,000–50,000 psi (230–345 MPa)

This determines how much force is required before the metal begins to deform permanently.
Armadura’s steel shingles are stamped into shape without cracking because the steel is engineered for high formability + high strength.

6.2 Tensile Strength

G90 steel provides a tensile strength around:

45,000–65,000 psi (310–450 MPa)

This measures the maximum pulling force the metal can withstand before breaking.
It matters for:

6.3 Elongation Percentage

Typical elongation values for roofing-grade G90 steel:

20–28%

This means the steel can stretch before breaking, which is essential during the stamping process used to form Armadura’s interlocking shingle geometry.

High elongation ensures:

6.4 Modulus of Elasticity

Steel’s modulus of elasticity (~200 GPa) determines how stiff the material is when bending forces are applied.

This is critical because Armadura roofing:


7. Corrosion Behavior of G90 in Canadian Climate

Corrosion is one of the most significant long-term threats to metal roofing. The performance of Armadura steel roofing relies heavily on how the zinc coating interacts with Canadian environmental conditions.

7.1 Zinc Patina Formation

Zinc undergoes a natural aging process:

  1. Fresh zinc reacts with oxygen → zinc oxide
  2. Zinc oxide reacts with moisture → zinc hydroxide
  3. Zinc hydroxide reacts with CO₂ → zinc carbonate
  4. Zinc carbonate forms a stable patina layer

This patina layer:

This is why Armadura metal roofing maintains its coating integrity for decades.


7.2 Winter Corrosion Resistance

Canadian winters contain:

G90 steel is designed to withstand these forces without:

Thinner coatings like G40 or G60 fail much sooner in these conditions.


8. Zinc Aging vs. Aluminum Oxidation (Armadura vs Aluminum Roofing)

Some metal roofing competitors use aluminum panels, which behave very differently.

8.1 Aluminum Oxidation

Aluminum forms:

This creates risks during:

8.2 G90 Zinc Aging (Armadura)

Zinc patina:

This is why Armadura steel roofing tends to outperform aluminum systems in Canadian climates.


9. G90 Steel Thickness in Armadura Roofing

G90 refers to the zinc coating weight, not the steel thickness.
However, Armadura uses structural-grade steel thickness optimized for:

Typical thickness ranges:

26–28 gauge for residential steel roofing (0.45–0.55 mm)

But the material feels more rigid because:


10. Surface Coatings Applied on G90 Steel

After galvanization, Armadura metal roofing receives an SMP (Siliconized Modified Polyester) coating.

The coating process includes:

  1. Chemical cleaning and pretreatment
  2. Primer application
  3. SMP crinkle finish topcoat
  4. High-temperature curing

Why this matters:

This is the coating that gives Armadura its long-term color stability and Canadian climate durability.

11. Structural Behavior of G90 Steel in Armadura® Shingle Geometry

One of the most important advantages of Armadura metal roofing is how its G90 steel substrate behaves once it is pressed into the interlocking shingle profile. The geometry of the shingle dramatically increases stiffness and structural resistance far beyond what the raw sheet thickness would suggest.

11.1 Profile Engineering

Armadura steel shingles include:

These shape elements increase the moment of inertia, which directly increases resistance to bending and deformation.

11.2 Structural Strength Multiplication

A flat sheet of G90 steel might flex under load —
but when stamped into the Armadura profile:

This is why a relatively thin gauge steel can outperform much thicker flat panels.


12. The Armadura Interlock System and Its Material Requirements

The interlocking system that Armadura uses requires steel with:

G90 steel meets these requirements perfectly.

12.1 Why G90 Is the Ideal Match for Interlocking Designs

Interlocking designs create areas of:

A thin zinc coating (G40 or G60) cannot survive these mechanical stresses without:

G90’s thick coating provides adequate sacrificial mass to survive decades of mechanical cycling in the interlocks.


13. Panel Expansion and Contraction Calculations (Thermal Movement)

All metal roofs expand and contract due to temperature changes.
But Armadura steel roofing moves significantly less because of:

13.1 Steel Thermal Expansion Formula

Steel expands at approx:

12 μm/m·°C

Example:
If a long metal sheet is 20 feet (6 meters) and experiences a 40°C temperature swing:

Expansion ≈ 12 × 6 × 40 = 2.88 mm of movement

This is why long panels shift, warp, or “oil-can.”

Armadura shingles solve this:

Armadura shingles are small.
Even with large temperature swings:

Expansion is typically:

0.2–0.4 mm per shingle

This is negligible.

Why this matters:


14. Armadura G90 Steel vs Imported Steel Roofing Products

Many imported metal roof systems use:

14.1 Problems with Imported Low-Grade Steel

Common failure points in cheaper metal roofing:

14.2 Advantages of Canadian G90 Steel

Armadura steel roofing:

This ensures long-term reliability in Canadian climates.


15. Why Canadian Manufacturing Matters for Armadura®

The performance of Armadura steel roofing is directly tied to the consistency of its manufacturing processes.

Canadian production ensures:

Imported systems often fail because they are designed for:

Armadura is engineered specifically for Northern conditions.


16. Zinc Layer Degradation Over Decades

G90 zinc does not stay at full thickness forever — it slowly degrades through natural oxidation.

Typical Zinc Erosion Rates

In Canadian conditions:

0.4–0.8 µm/year

Given zinc layer thickness (approx 20–25 µm):

Expected corrosion protection lasts:

30–55 years before substrate exposure

But with SMP coating and proper interlocks, total lifespan extends to:

50–70+ years

This is exactly why Armadura steel roofing outlasts:

17. SMP Coating Chemistry on Armadura® G90 Steel

The SMP (Siliconized Modified Polyester) coating applied to Armadura metal roofing is a multilayer protective system designed to shield the G90 galvanized steel substrate from UV radiation, moisture, abrasion, and thermal cycling.

17.1 Composition of SMP Coatings

Typical SMP coatings used in Canadian manufacturing include:

This formulation provides a durable, flexible finish that outperforms older acrylic or polyester-only coatings.


17.2 Role of Silicon Additives

Silicon increases:

SMP coatings maintain flexibility even at temperatures below –20°C, which is essential for Canadian roofing exposed to freeze–thaw cycles.

Benefits for Armadura steel roofing:


18. Adhesion Strength and Curing Process

Before the SMP topcoat is applied, G90 steel undergoes:

  1. Surface cleaning
  2. Chemical pretreatment
  3. Primer coating
  4. High-temperature oven curing

18.1 Why High-Temperature Curing Matters

Curing bonds the SMP coating directly into:

This creates a single integrated surface layer rather than a simple film.

This improves:


19. G90 Zinc Edge Protection (Cut-Edge Corrosion Resistance)

One of the greatest advantages of G90 galvanized steel is its cut-edge protection.

When a piece of Armadura steel roofing is cut:

This is known as galvanic healing.

Why this matters:

Every Armadura steel shingle requires cutting near:

With G90 zinc mass:

G40 or G60 coatings do NOT protect cut edges long-term.


20. G90 vs. Galvalume: Which Is Better for Canada?

Some metal roofing systems use Galvalume, an aluminum-zinc alloy coating.

20.1 Galvalume Composition:

20.2 Advantages of Galvalume

20.3 Disadvantages in Canadian Climates

Why Armadura uses G90 instead of Galvalume


21. SMP Coating and Long-Term Weather Resistance

The SMP coating on Armadura roofing protects against:

21.1 Color Stability

SMP coatings typically maintain:

Even after 20–30 years.

This is why Armadura roofing maintains a clean, crisp appearance decades into its lifespan.


22. How G90 and SMP Work Together

The combination of:

G90 zinc layer + SMP coating

creates a two-tiered defense system:


Tier 1 — SMP Coating (outer layer)

Protects against:

Tier 2 — G90 Zinc (inner layer)

Protects against:


Why the combination matters:

Most metal roofing failures begin when:

Armadura prevents all three failure pathways.

23. Failure-Mode Resistance in Armadura® G90 Steel Roofing

A roofing system’s durability is defined not only by how it performs under normal conditions but by how it resists failure modes — the mechanisms by which roofing materials deteriorate over time.
Armadura metal roofing, through its G90 galvanized steel composition and SMP coating, provides resistance across all major roofing failure types.

Below is an engineering breakdown.


23.1 Moisture-Driven Failure (Water Absorption & Rust)

Asphalt

Armadura G90 Steel

Result: No structural moisture failure over decades.


23.2 UV & Solar Radiation Failure

Asphalt

Armadura Steel Roofing

Result: UV-resistant for 30–40+ years.


23.3 Thermal Movement Failure (Expansion/Contraction)

Large metal sheets expand significantly.

Standing Seam / Long Panels

Armadura Interlocking Shingles

Result: Extremely stable under thermal cycling.


23.4 Impact Failure (Hail, Debris)

Asphalt

Aluminum Roofing

Armadura G90 Steel

Result: Strong impact resistance in severe weather.


23.5 Wind Uplift Failure

Asphalt Shingles

Armadura Steel Roofing

Result: Superior wind uplift resistance.


24. Long-Term Zinc Erosion Modeling (50–70+ years)

Corrosion scientists estimate zinc erosion under Canadian conditions at:

0.4–0.8 microns per year
depending on humidity, exposure, salt levels, and orientation.

G90 thickness per side:

15–20 microns

Expected protective lifespan:

25–40 years per side, or
50–70+ years total
before zinc is fully consumed at any exposed edge.

This matches the expected lifespan of Armadura steel roofing in real-world installations.


25. G90 Aging vs SMP Aging

SMP Coating (outer layer)

G90 Zinc (inner layer)

Combined Effect

The SMP layer reduces zinc erosion significantly:

This extends roofing lifespan beyond that of G90 alone.


26. SMP Texture and Its Functional Benefits

The Armadura crinkle-texture SMP coating is not only aesthetic. It provides engineering benefits:

Traction Behavior

Surface Strength

Coating Thickness Uniformity

Crinkle finish adds micro-ridges:

This improves long-term performance under Canadian conditions.


27. Armadura G90 Steel and Winter Climate Performance

Key winter considerations:

Freeze–Thaw Cycles

Snow Load

Ice Damming

Wind Chill

Result: Best-in-class winter reliability.


28. G90 Steel and Summer Heat Performance

Heat Exposure in Canadian Summers:

SMP’s heat behavior:

Steel substrate behavior:

Combined:
Armadura roofing performs predictably in extreme heat.

29. Comparative Material Tables for Roofing Science

Below are the definitive engineering comparisons showing why G90 galvanized steel, as used in Armadura metal roofing, is the optimal roofing substrate for Canadian climates.


Table 1 — Corrosion Protection Comparison

Material TypeCoatingCorrosion ResistanceWinter PerformanceEdge Protection
Armadura G90 Steel90 g/m² zincExcellentExcellentStrong
G60 Steel60 g/m² zincModerateFairWeak
G40 Steel40 g/m² zincLowPoorVery Weak
Galvalume (AZ55)Aluminum-ZincHigh in dry climatesModerate in coldLow
AluminumOxide LayerModerateBrittle in winterPoor

Table 2 — Structural Behavior Comparison

PropertyArmadura G90 SteelAluminum RoofingAsphalt Shingles
RigidityHighLowVery Low
Dent ResistanceHighVery LowN/A
Thermal MovementLowHighMedium
Moisture Absorption0%0%High
Freeze–Thaw ToleranceExcellentModerateVery Poor

Table 3 — Coating Durability Comparison

Coating TypeUV ResistanceChalk/FadeFlexibility in WinterHeat Durability
SMP Crinkle Finish (Armadura)ExcellentLowExcellentExcellent
Standard PolyesterModerateMediumPoorFair
PVDF (Kynar)ExcellentVery LowModerateExcellent
AcrylicLowHighPoorPoor

30. Long-Term Aging Behavior of Armadura® G90 Steel

The combined aging curve of G90 zinc + SMP coating follows a predictable pattern:

Stage 1 — First 10 Years

Stage 2 — 10 to 25 Years

Stage 3 — 25 to 45 Years

Stage 4 — 45 to 70+ Years

This aligns with the real-world performance expectations of Armadura steel roofing in Canada:
50–70+ years of functional life.


31. Canadian Climate Advantage: Why G90 Is Superior in the North

Canada’s climate is one of the harshest in the world for roofing systems.

Key environmental hazards:

G90 steel + SMP coating withstands all of these due to:


32. Comprehensive Summary: Why Armadura® Uses G90 Steel

Armadura steel roofing is engineered using G90 galvanized steel because:

Structural Benefits

Corrosion Benefits

Coating Benefits

Climate Benefits

Longevity Benefits

Together, these properties create one of the most durable and climate-appropriate roofing materials available in North America.


33. Conclusion

The use of G90 galvanized steel in Armadura® metal roofing is not incidental — it is fundamental to the roofing system’s performance, engineering reliability, and long-term durability.
G90 provides:

This deep technical advantage is one reason Armadura metal roofing has become one of Canada’s most engineered roofing systems for harsh climates and heavy snow regions.


Learn More at ROOFNOW™ Knowledge Center

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Recommended Reading (Amazon)

📘 The Real Cost of a Cheap Roof — Paperback
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📗 Roof Smart. Roof Once. — FREE Kindle Edition
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