I. Introduction
Steel structure bridges are an important component of modern transportation infrastructure. Due to prolonged exposure to atmospheric conditions, steel bridges face severe corrosion threats. A well-designed anticorrosive coating system is key to ensuring the design service life of the bridge.
II. Corrosion Environment Classification (ISO 12944)
Corrosion Level | Typical Environment | Carbon Steel Corrosion Rate
C1 (Very Low) | Indoor, dry environment | ≤1.3 μm/year
C2 (Low) | Rural atmosphere | 1.3–25 μm/year
C3 (Medium) | Urban/industrial atmosphere | 25–50 μm/year
C4 (High) | Coastal/chemical plants | 50–80 μm/year
C5 (Very High) | Heavy pollution/marine | 80–200 μm/year
III. Design of Anticorrosive Coating System for Bridges
Example of a typical coating system for C4 environment:
Surface preparation: Abrasive blasting to Sa2.5 grade, roughness Rz 40–75 μm
Primer (zinc-rich epoxy): Dry film thickness 60–80 μm, provides cathodic protection
Intermediate coat (micaceous iron oxide epoxy): Dry film thickness 100–150 μm, barrier protection, increases coating thickness
Topcoat (polyurethane/fluorocarbon): Dry film thickness 60–80 μm, weather resistance, decoration, protects underlying layers
Total dry film thickness: 220–310 μm, design service life: 15–25 years.
IV. Kexin Bridge Anticorrosion Products
Kexin New Materials offers a full range of bridge anticorrosion coatings, which have been successfully applied in several key bridge projects. The products have passed tests by the National Coating Quality Supervision and Inspection Center, and their performance meets the requirements of the JT/T 722 standard.
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