Professional surface treatment and coating systems for steel structures, designed to protect against corrosion in various environmental conditions. From basic primer to heavy-duty multi-layer systems, we provide coating solutions per ISO 12944 standards with guaranteed protection life of 15-25+ years.
| Class | Environment | Typical Locations | Recommended System |
|---|---|---|---|
| C1 | Very low | Heated buildings, clean air (offices, schools) | Single coat primer (40μm) |
| C2 | Low | Unheated buildings, rural areas, low humidity | Primer + finish (80-120μm) |
| C3 | Medium | Urban/industrial areas, moderate humidity, warehouses | Epoxy primer + PU finish (160-200μm) |
| C4 | High | Coastal areas, chemical plants, high humidity, polluted industrial | Epoxy zinc-rich + epoxy mid + PU/fluorocarbon (240-320μm) |
| C5-M | Very high (marine) | Offshore, coastal splash zones, aggressive chemical, salt spray | Hot-dip galvanizing + epoxy + fluorocarbon (320-400μm+) |
Centrifugal wheel blasting to SA 2.5 (near-white metal) per ISO 8501-1. Removes all mill scale, rust, and contaminants, creating a 40-75μm anchor profile for optimal coating adhesion.
For site touch-ups and repair areas. Power tool cleaning to St 3 per ISO 8501-1, removing all loose rust and mill scale. Used for field repairs and inaccessible areas.
Pre-cleaning to remove oil, grease, and cutting fluids prior to blasting. Ensures no contamination is embedded in the steel surface during blasting.
Replica tape or profilometer verification of surface roughness (40-75μm for paint systems, 75-100μm for galvanizing). Test reports included with every batch.
| Parameter | Specification |
|---|---|
| Standard | ASTM A123, EN ISO 1461, GB/T 13912 |
| Coating Thickness | ≥85μm for steel >6mm; ≥65μm for 3-6mm; ≥55μm for 1.5-3mm |
| Zinc Purity | ≥98.5% pure zinc bath |
| Protection Life | 20-50 years depending on environment (C2-C4) |
| Best For | Primary structural members, outdoor exposure, coastal areas, maintenance-free applications |
| System | Layers | Total DFT | Environment | Protection Life |
|---|---|---|---|---|
| Basic | Red oxide primer (1 coat) | 40-60μm | C1-C2 (indoor, rural) | 5-8 years |
| Standard | Epoxy primer + alkyd/PU finish | 120-160μm | C2-C3 (urban, standard industrial) | 10-15 years |
| Heavy-Duty | Zinc-rich epoxy primer + epoxy mid coat + PU finish | 200-280μm | C3-C4 (coastal, chemical, high humidity) | 15-20 years |
| Premium | Galvanized + epoxy zinc-rich + epoxy mid + fluorocarbon finish | 300-400μm | C4-C5M (marine, offshore, aggressive chemical) | 20-25+ years |
A: Hot-dip galvanizing provides 20-50 year protection with zero maintenance, but costs 30-50% more upfront and cannot be easily repaired on-site. Paint systems are cheaper, can be field-repaired, and offer color options, but require repainting every 10-20 years. For primary structural members in outdoor/coastal environments, we recommend galvanizing. For secondary members and color-coded buildings, paint systems are more cost-effective. Many projects use a combination: galvanized primary frames + painted secondary members.
A: Yes, galvanized steel can be painted, but requires proper surface preparation. The galvanized surface must be cleaned (sweep blast or chemical treatment) to remove the smooth zinc oxide layer, then a compatible primer (epoxy or polyurethane) is applied before the finish coat. Direct painting on untreated galvanizing will result in poor adhesion and premature peeling. We provide "duplex coating" (galvanizing + paint) for maximum protection life.
A: For coastal areas (C4-C5M environment), we recommend: hot-dip galvanizing (85μm+) + epoxy zinc-rich primer (60-80μm) + epoxy intermediate coat (100-120μm) + polyurethane or fluorocarbon finish (60-80μm), total DFT 300-400μm. This system provides 20-25+ years of protection in salt spray environments. For offshore or splash zone applications, additional consideration should be given to immersion-grade epoxies and glass flake reinforcement.
A: Coating typically adds 8-25% to the total steel structure cost: basic red oxide primer adds ~8%, standard epoxy+PU system adds ~12-15%, heavy-duty 3-coat system adds ~18-22%, hot-dip galvanizing adds ~20-25%. However, proper coating reduces maintenance costs by 50-70% over the building lifecycle and extends structural life by 2-3x. We recommend budgeting for the coating system appropriate to your environment rather than choosing the cheapest option, as premature coating failure leads to costly repainting and potential structural degradation.
A: Yes, field coating is possible but generally more expensive and lower quality than shop coating. Shop application provides controlled environment (temperature, humidity, dust control), proper surface preparation (automatic shot blasting), and consistent film thickness. Field coating is typically used for: touch-up of damaged areas during installation, connection points that cannot be coated in shop, and maintenance/repainting of existing structures. We recommend 95%+ of coating be completed in the factory, with only field touch-ups on-site.
Our corrosion engineers will recommend the optimal coating system based on your project location, environment, and budget. Get a coating specification and quote within 24 hours.