The core of application standards for color-coated steel coils lies in matching the base material, coating type, thickness, and performance indicators to the scenario environment (e.g., outdoor/indoor, corrosive/dry). The key standards for three core scenarios are specified below:
1. Construction Field (Mainly Outdoor: Roofs/Walls of Factories/Warehouses, Modular Buildings)
– Base Material Selection: Prioritize hot-dip aluminum-zinc coated steel sheets (with weather resistance 2-5 times that of hot-dip galvanized sheets) or hot-dip galvanized sheets with high zinc coating (double-sided zinc coating ≥180g/㎡; ≥275g/㎡ for coastal/high-corrosion areas). Cold-rolled base materials are prohibited (prone to rust).
– Coating Standards:
– Ordinary environment (inland dry areas): Choose PE coating (weather resistance: 5-8 years), with upper surface coating thickness ≥20μm.
– Harsh environment (coastal, high-humidity, strong UV areas): Choose HDP (weather resistance: 8-12 years) or PVDF coating (weather resistance: 15-20 years), with upper surface coating thickness ≥25μm. It must comply with the “external construction use” grade specified in GB/T 12754 Color-Coated Steel Plates and Strips.
– Additional Requirements: Must pass the salt spray resistance test (≥500 hours without obvious corrosion for coastal areas) and artificial aging resistance test (≥1000 hours without chalking/discoloration).
2. Home Appliance Field (Mainly Indoor: Shells of Refrigerators/Washing Machines, Outdoor Units of Air Conditioners)
– Base Material Selection: For indoor dry scenarios, use cold-rolled base materials or hot-dip galvanized sheets with thin zinc coating (double-sided zinc coating: 50-80g/㎡); for semi-outdoor scenarios such as air conditioner outdoor units, use hot-dip galvanized sheets (zinc coating ≥120g/㎡).
– Coating Standards:
– Internal parts (e.g., internal partitions of refrigerators): Choose ordinary PE coating, with thickness ≥15μm. It must comply with the “internal construction use” or “home appliance internal use” grade, with focus on adhesion (cross-cut test ≥Grade 1).
– External parts (e.g., washing machine panels): Choose modified PE or SMP coating, with thickness ≥18μm. It must pass the damp-heat resistance test (≥500 hours without blistering) and scratch resistance test (hardness ≥3H).
– Additional Requirements: Color uniformity (color difference ΔE ≤1.5) and gloss deviation (±5°) must comply with the appearance standards of the home appliance industry.
3. Transportation Field (Semi-Outdoor/Mobile Scenarios: Carriage Panels, Containers, Agricultural Machinery Shells)
– Base Material Selection: All use hot-dip aluminum-zinc coated steel sheets (aluminum-zinc content ≥150g/㎡) or hot-dip galvanized sheets (zinc coating ≥275g/㎡) to resist vibration, friction, and outdoor corrosion.
– Coating Standards: Choose SMP or PVDF coating, with upper surface thickness ≥25μm. It must comply with the relevant requirements for “weather-resistant structural steel” in GB/T 3274 Hot-Rolled Thick Steel Plates and Strips for Carbon Structural Steel and Low-Alloy Structural Steel, and pass the impact resistance test (≥5J without coating peeling) and bending resistance test (bending radius ≤2 times the plate thickness without cracks).
– Additional Requirements: Color-coated coils for containers must additionally meet the anti-rust and weather resistance provisions in ISO 1496-3 Containers – Specification and Testing – Part 3: General Purpose Containers.