(DPS) Dual-Layer Epoxy Anti-Corrosion Powder Coating

Surface Finish Options Overview

Product Introduction:
This dual-layer epoxy powder coating system is carefully formulated using special epoxy resins and functional curing agents. The base layer, like other epoxy anti-corrosion powder coatings, offers excellent anti-corrosion properties. The outer layer, while maintaining anti-corrosion properties, enhances protective performance. Compared to a three-layer PE structure, it offers a lower comprehensive anti-corrosion cost.

Product Usage:
Suitable for complex anti-corrosion environments, especially pipelines crossing through mountainous, river, and hilly areas.

Product Features:

Excellent adhesion between the base material and the epoxy layers.Strong resistance to permeation and corrosion with high curing completion rate.High hardness of the outer coating, dense coating, scratch-resistant, and good resistance to plant root penetration.Excellent high-temperature cathodic disbondment resistance and superior mechanical properties.

Powder Performance:

Powder Coating Performance Parameters

Test Item	Technical Specification	Remarks
Appearance	Uniform color, no lumps	Visual inspection
Particle Size Distribution	Residuals ≤4.0 at 150um, ≤0.2 at 250um	Q/CNPC 38-2002 Appendix C
Volatile Content (%)	≤0.6	Q/CNPC 38-2002 Appendix B
Gellation Time at 205±3°C (s)	≥12	Q/CNPC 38-2002 Appendix A
Curing Time at 230°C (min)	≤3	SY/T 0315-2005
Magnetic Substance Content (%)	≤0.002	GB/T 6570

Cured Powder Coating Performance Parameters

Test Item	Technical Specification	Remarks
Appearance	Smooth, uniform color, no bubbles, no cracks, allows slight orange peel	Visual inspection
Adhesion (Grade)	1-2	SY/T 0315-2005
Negative Electrode at 24h (mm)	≤6.5	SY/T 0315-2005
Negative Electrode at 28d (mm)	≤8	SY/T 0315-2005
Cross-sectional Crack Rate	1-4	SY/T 0315-2005
Coating Surface Porosity Rate	1-4	SY/T 0315-2005
Bending Resistance (3°)	No cracks	SY/T 0315-2005
Volume Resistivity	≤1*10¹³	GB/T 1410
Electric Strength (MV/m)	≥30	GB/T 1408.1
Impact Resistance (1.5J at -30°)	No leakage points	SY/T 0315-2005
Chemical Resistance	Qualified	SY/T 0315-2005
Wear Resistance (Abrasion Method)	≤3	SY/T 0315-2005
Salt Spray Test (1000h)	Coating shows no change	GB/T 1771-1991

Execution Standard:
Q/CNPC 38-2002 “Technical Specification for Double Layer Fusion Bonded Epoxy Powder Coating on Steel Pipes”

Curing Conditions:

Property	Specification	Remarks
Temperature	200-230°C for 3-1.5 minutes	Medium-frequency heating recommended

Application Parameters:

Parameter	Specification	Notes
Applicable Equipment	Frictional charging spray, corona electrostatic spray
Film Thickness	250-500um	Adjustable according to workpiece requirements

Storage Period:

The product can be stored for 6 months in dry conditions below 30°C.The used coating must be re-sealed immediately to prevent moisture absorption affecting performance.Packaging: 20kg paper boxes lined with plastic bags.

FAQ

1. What is Powder Coating?

Powder coating is a dry finishing process used to apply a protective and decorative coating on metal or other surfaces. Instead of using liquid paint, fine powder particles (usually made of polyester, epoxy, or hybrid resins) are electrostatically charged and sprayed onto a conductive surface. The coated object is then baked in an oven, where the powder melts, flows, and cures into a smooth, durable finish.

Key features:

Durable, hard finish

Resistant to scratches, corrosion, and UV

Environmentally friendly (no VOCs)

2. Benefits of Powder Coating

Powder coating offers several advantages over traditional liquid painting:

Durability: Resistant to chipping, scratching, fading, and wear.

Corrosion Protection: Provides excellent protection against rust and chemicals.

Environmentally Friendly: No volatile organic compounds (VOCs) and minimal waste.

Efficiency: Overspray can be collected and reused, up to 99% material utilization.

Uniform Finish: Smooth, even coating without runs or drips.

Cost-Effective: Single-coat systems can achieve high film thickness, reducing labor and energy.

Aesthetic Variety: Wide range of colors, textures, and effects.

3. What Temperature to Cure Powder Coating

The curing temperature depends on the type of powder used:

Epoxy powder: ~160–200°C (320–392°F)

Polyester powder: ~180–210°C (356–410°F)

Hybrid (Epoxy-Polyester) powder: ~180–200°C (356–392°F)

Typical curing time: 10–20 minutes depending on thickness and oven type.

Always follow the powder manufacturer’s specifications for best results.

4. Process for Powder Coating

The powder coating process usually follows these steps:

Surface Preparation:

Clean the surface thoroughly (remove oil, grease, rust, or dirt)

Methods: chemical cleaning, sandblasting, or phosphating

Pre-Treatment:

Apply a conversion coating or primer if needed to improve adhesion

Powder Application:

Spray the powder using an electrostatic spray gun or fluidized bed

Curing:

Bake the coated object in an oven at the recommended temperature for the powder type

The powder melts and forms a continuous, smooth film

Cooling & Inspection:

Let the coated item cool

Inspect for defects, uniform coverage, and desired thickness

5. How to Spray Powder Coat

Equipment Needed:

Electrostatic spray gun

Compressed air supply

Powder feed hopper or container

Grounding of the object

Steps:

Ground the object: Ensures the charged powder is attracted to the surface.

Spray evenly: Hold the gun 6–12 inches from the surface, moving in smooth, overlapping strokes.

Apply sufficient powder: Ensure full coverage without excessive buildup.

Cure immediately: Transfer the sprayed item to the curing oven to fuse the powder into a solid coating.

Tips:

Maintain consistent speed and distance while spraying.

Use proper ventilation to reduce airborne powder accumulation.

Test a small area to check film thickness and color before full application.