Is Sandblasting Before Painting Required and What Should Be the Paint Scheme in PEB?
Pre-Engineered Buildings (PEBs) are widely used for industrial, commercial, and warehousing applications. While design, fabrication, and erection often get the most attention, one critical factor that directly affects the life of a PEB is its surface preparation and paint system.
Among these, a common question arises:
“Is sandblasting before painting required?”
And equally important:
“What should be the correct paint scheme for a long-lasting PEB?”
Let’s break it down with clarity and industry insights.
Is Sandblasting Before Painting Required in PEB?
Short Answer: Yes — ideally.
Sandblasting (also called abrasive blasting) is the most recommended and industry-standard method for preparing steel surfaces before painting.
Why is it needed?
Because structural steel comes with mill scale, rust, oil, and impurities. If not removed properly, the paint will not bond well, leading to:
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Premature rusting
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Flaking or peeling paint
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Reduced building life
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Increased maintenance cost
Sandblasting achieves a clean, roughened surface profile that helps the paint anchor firmly.
Benefits of Sandblasting Before Painting
1. Removes Rust & Mill Scale Completely
PEB frames typically develop rust during storage and transportation. Sandblasting ensures the steel surface is fully cleaned.
2. Improves Paint Adhesion
Paint grips better on a rough, clean profile, improving durability.
3. Increases Corrosion Resistance
A well-prepared surface resists moisture, chemical exposure, and environmental damage.
4. Enhances Paint Life by 50–70%
Sandblasted surfaces significantly extend the life of the coating system.
5. Ensures Uniform Paint Thickness
A smooth, uncontaminated surface allows a consistent DFT (Dry Film Thickness).
What if Sandblasting Is Not Possible?
In some cases (budget constraints or site limitations), manufacturers may skip sandblasting.
Alternatives include:
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Mechanical cleaning (hand tools, grinders)
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Power tool cleaning (stainless steel brushes, rotary tools)
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Chemical cleaning / degreasing
However, none of these methods match the quality and longevity of proper abrasive blasting.
Recommended Surface Preparation Standard
For structural steel in PEBs, the recommended international standard is:
SA 2.5 (Near White Metal Blast Cleaning)
This grade ensures:
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95% of mill scale removed
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Bare metal exposed
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Minimum contaminants
This is the ideal preparation level for industrial-grade coatings.
What Should Be the Paint Scheme in PEB?
A PEB paint scheme must be designed based on:
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Environmental conditions
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Corrosion category (C1, C2, C3, C4, C5)
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Expected building life
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Budget & maintenance cycles
Here is a commonly accepted, high-performance PEB paint system:
Standard Paint Scheme for PEB Structures
1. Primer Coat
Epoxy Zinc-Rich Primer (40–60 microns)
Purpose:
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Excellent corrosion resistance
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Acts as sacrificial protection
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Strong adhesion on blasted steel
Zinc-rich primers are considered the best base layer for long-term structural durability.
2. Intermediate Coat
Epoxy Intermediate / MIO Epoxy Coat (60–100 microns)
Purpose:
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Builds thickness
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Improves barrier protection
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Provides mechanical strength
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Withstands industrial pollutants
MIO (Micaceous Iron Oxide) enhances hardness and abrasion resistance.
3. Top Coat
Polyurethane (PU) Finish Coat (40–60 microns)
Purpose:
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UV resistance
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Gloss & color retention
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Weather durability
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Protection against fading, chalking, and chemical exposure
PU is the preferred topcoat for outdoor steel surfaces.
Ideal Total DFT (Dry Film Thickness)
Minimum: 140–200 microns
Higher DFT is recommended for coastal, chemical, or high-humidity zones.
Special Paint Schemes for High-Corrosion Areas
For coastal regions or fertilizer plants:
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Zinc-rich primer
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High-built epoxy
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PU topcoat
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Optional: polyurethane clear coat
For heavy industrial environments:
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Zinc silicate primer
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Epoxy intermediate
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Epoxy topcoat (chemical resistant)
Conclusion
Sandblasting is not just recommended — it is one of the most critical steps to ensure long-lasting performance of paint on PEB structures. Proper surface preparation followed by a well-designed multi-coat paint scheme significantly enhances the building’s life, reduces maintenance, and protects your investment.
By choosing the right combination of:
✔ Sandblasting (SA 2.5)
✔ Zinc-rich primer
✔ Epoxy intermediate coat
✔ Polyurethane topcoat
You ensure that your PEB remains durable, corrosion-resistant, and aesthetically stable for decades.
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