Steel Coil Surface Treatment Technologies
A Comprehensive Guide to Steel Coil Processing Techniques and Production Workflows
Overview of Steel Coil Surface Treatments
Steel coil surface treatment is a critical process that enhances corrosion resistance, improves paint adhesion, and extends the service life of steel products. Hengze Steel offers advanced treatment options including galvanizing, galvalume coating, and color coating to meet diverse industrial needs.
Types of Surface Treatments for Steel Coils
Galvanized (GI) Coating
Hot-dip galvanizing process with controlled zinc layer thickness; offers corrosion and weather resistance; widely used in construction, automotive, and home appliance manufacturing.
Galvalume (GL) Coating
55% aluminum and 45% zinc alloy coating for superior corrosion resistance; longer service life and better reflectivity than GI; ideal for roofing, wall panels, and storage tanks.
Pre-painted (PPGI / PPGL)
Pre-treatment, coating application, and oven curing process; available in various colors and textures; suitable for decorative use and chemical-resistant environments.
Surface Preparation Techniques
Cleaning & Degreasing
Remove oil & dirt
Pickling
Remove oxide scale
Chemical Conversion Coating
Enhance adhesion
Drying
Prepare for coating
Performance Comparison Table
| Property | GI (Galvanized) | GL (Galvalume) | PPGI (Pre-painted GI) | PPGL (Pre-painted GL) |
|---|---|---|---|---|
| Corrosion Resistance | Good | Very Good | Very Good | Excellent |
| Cost | Low | Medium | Med-High | High |
| Lifespan | 15–20 yrs | 20–25 yrs | 20–25 yrs | 25–30 yrs |
| Aesthetic Options | Zinc finish | Metallic finish | Colors/textures | Colors + metallic |
| Applications | Construction, auto | Roofing, marine | Panels, appliances | Premium roofing, facades |
Quality Standards & Testing Methods
| Standard Code | Full Name | Scope |
|---|---|---|
| ASTM A653 | Standard Specification for Steel Sheet, Zinc-Coated (Galvanized) or Zinc-Iron Alloy-Coated (Galvannealed) by the Hot-Dip Process | Covers GI and Galvannealed coatings in the US market |
| JIS G3302 | Hot-dip Zinc-Coated Steel Sheet and Strip | Japanese standard for GI coatings |
| JIS G3321 | Hot-dip 55% Aluminum-Zinc Alloy-Coated Steel Sheet and Strip | Japanese standard for GL coatings |
| EN 10346 | Continuously Hot-Dip Coated Steel Flat Products | European standard for GI, GL, and other metallic coatings |
| GB/T 2518 | Continuous Hot-Dip Zinc-Coated Steel Sheet and Strip | Chinese standard for GI coatings |
| GB/T 2518-2008 | Hot-Dip Al-Zn Coated Steel Sheet | Chinese standard for GL coatings |
Common Testing Methods for Surface-Coated Steel
Coating Thickness Measurement
Purpose: Verify coating meets required thickness for protection.
Method: Use magnetic induction or eddy current (non-destructive).
Salt Spray Test (Corrosion Resistance)
Purpose: Simulate harsh conditions to check corrosion resistance.
Method: Expose in salt fog chamber (ASTM B117 / ISO 9227).
Adhesion Test (Paint/Coating Bond)
Purpose: Check how firmly coating adheres to substrate.
Method: Cross-hatch cut and tape pull-off (ASTM D3359 / ISO 2409).
Applications in Various Industries
Construction
Roofing sheets, wall cladding, structural purlins, steel
Automotive
Body panels, chassis structures, and underbody protection parts.
Home Appliances
Refrigerator doors, washing machine panels, and oven shells.
Industrial Equipment
Machine casings, storage racks, and protective enclosures.
Why Choose Hengze Steel for Surface Treatment
Own Manufacturing Facilities – We operate advanced hot-dip galvanizing, Al-Zn coating, and color coating production lines to ensure consistent quality and fast delivery.
Strict Multi-Stage Quality Control – From raw material inspection to final surface treatment tests (thickness, adhesion, salt spray), every step meets ASTM, JIS, EN, and GB standards.
Tailor-Made Coating Solutions – Customized coating thickness, colors, and finishes to match specific application needs in construction, automotive, appliances, and industrial sectors.
Proven Industry Experience – Years of supplying to global markets with stable quality, competitive pricing, and professional technical support.
Technical Resources & Downloads
Surface Treatment Navigation
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Surface Treatment OverviewSurface Treatment Overview
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Types of Surface TreatmentsTypes of Surface Treatments
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Surface Preparation TechniquesSurface Preparation Techniques
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Performance Comparison TablePerformance Comparison Table
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Quality Standards & TestingQuality Standards & Testing
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Industry ApplicationsIndustry Applications
