Service Life & Selection Guide of Color Coated Steel Sheets

I. Service Life of Color Coated Steel Sheets

1. Ordinary Civil Grade
   
   
   The base plate is cold-rolled steel sheet with single/ thin coating, suitable for temporary buildings (e.g., construction site prefabricated houses).
   
   
   Service life: 5–10 years. Coating fading and rusting are prone to occur.
2. Industrial Standard Grade
   
   
   The base plate is hot-dip galvanized/galvalume steel sheet, with polyester (PE) or silicone-modified polyester (SMP) coating. It is applicable to workshops and warehouses.
   
   
   Service life: 10–20 years. It has moderate weather resistance and is suitable for dry or slightly corrosive environments.
3. High-end Weather-resistant Grade
   
   
   The base plate is galvalume steel sheet (zinc-aluminum content ≥55%) with polyvinylidene fluoride (PVDF) coating. It is designed for coastal areas, highly corrosive industrial zones or high-end building exterior walls.
   
   
   Service life: 20–30 years. It boasts excellent UV resistance, acid-alkali resistance and salt spray resistance.

II. Selection Method of Color Coated Steel Sheets

1. Clarify the Service Scenario

• Temporary buildings (prefabricated houses): Choose ordinary cold-rolled base plate + PE coating for cost-effectiveness.
• Industrial workshops/warehouses: Opt for hot-dip galvanized base plate (zinc coating weight ≥80g/㎡) + SMP coating to balance cost and durability.
• Coastal/highly corrosive environments: Select galvalume base plate + PVDF coating. Ensure the coating thickness is ≥25μm and fluorine content is ≥70%.

2. Verify Base Plate Quality

• Prioritize hot-dip galvanized/galvalume base plates and avoid cold-galvanized ones (prone to rusting).
• Check the zinc coating weight: ≥60g/㎡ for civil use, ≥80g/㎡ for industrial use, and ≥120g/㎡ for coastal areas.

3. Distinguish Coating Processes

4. Inspect Appearance and Details

• Surface: The coating should be uniform without bubbles, scratches or missed coating areas, and the color should be consistent.
• Edges: The cutting surface should be burr-free, and the base plate should be free from oxidation and rust.
• Certification: Prefer products with ISO 9001 certification and SGS salt spray test report to ensure qualified coating adhesion.

5. Match Plate Profile and Thickness

• For roofing: Choose plates with wave height ≥30mm to enhance load-bearing capacity and drainage performance, with base plate thickness ≥0.4mm.
• For wall cladding: Flat or small-wave profile plates are acceptable, with base plate thickness ranging from 0.3mm to 0.4mm.