YS STEEL produces Prepainted Steel Coils through a multi-stage process that begins with substrate cleaning and ends with a fully cured, formable paint film. The process is designed to remove surface contaminants, stabilize the metallic coating, and create a strong chemical bond between the steel surface and the organic coating layers. A typical production flow includes the following steps:
The coating system selection is based on end-use exposure, forming severity, and budget. YS STEEL offers four main resin families: polyester, silicone modified polyester, high durability polyester, and polyvinylidene fluoride. Each resin has a specific balance of flexibility, hardness, UV resistance, and chemical resistance.
The table below summarizes the standard product range available from YS STEEL. Custom dimensions and special coating systems can be produced after technical review.
| Parameter | Standard Value | Optional or Custom Range |
|---|---|---|
| Substrate | Hot-dip galvanized steel, hot-dip galvalume steel, cold rolled steel | High-strength grades, structural steel |
| Thickness | 0.14 mm to 0.80 mm | 0.12 mm to 1.50 mm |
| Width | 914 mm, 1000 mm, 1200 mm, 1219 mm, 1250 mm | 600 mm to 1250 mm, slit to 30 mm minimum |
| Coil inner diameter | 508 mm | 610 mm |
| Coil weight | 3 to 5 metric tons | 3 to 8 metric tons |
| Top paint type | PE, SMP, HDP, PVDF | Polyurethane, acrylic, epoxy-modified systems |
| Top coat dry film thickness | 15 to 25 microns | 25 to 35 microns for PVDF or high-build systems |
| Primer dry film thickness | 5 to 8 microns | Epoxy or polyurethane primer |
| Back coat dry film thickness | 5 to 10 microns | One-coat or two-coat back coating |
| Color system | RAL, PANTONE, custom solid colors | Metallic, wood grain, marble, brushed, matte, textured |
| Zinc coating mass | Z60 to Z275 g/m² | Z30 to Z350 g/m² |
| Alu-zinc coating mass | AZ70 to AZ150 g/m² | AZ40 to AZ200 g/m² |
The performance differences between paint systems are mainly related to UV resistance, flexibility, hardness, and service life. The following table provides comparative data for standard YS STEEL coating options.
| Paint Type | Typical Top Coat Thickness | Pencil Hardness | T-Bend Flexibility | UV Resistance | Recommended Environment |
|---|---|---|---|---|---|
| PE (Polyester) | 15 to 20 microns | HB to F | 3T to 4T | Good | General interior and mild exterior |
| SMP (Silicone Modified Polyester) | 18 to 22 microns | F to H | 2T to 3T | Very good | Industrial and moderate coastal |
| HDP (High Durability Polyester) | 20 to 25 microns | H to 2H | 1T to 2T | Excellent | High UV, chemical exposure, exterior cladding |
| PVDF (Polyvinylidene Fluoride) | 25 to 35 microns | H to 2H | 1T | Superior | Premium facades, coastal, high UV regions |
Mechanical behavior depends on the base metal and its metallic coating. YS STEEL selects substrate grades according to the final forming operation and structural requirement.
| Substrate | Yield Strength (MPa) | Tensile Strength (MPa) | Elongation (%) | Typical Use |
|---|---|---|---|---|
| Galvanized DX51D | 140 to 280 | 270 to 500 | ≥ 22 | Roofing, wall cladding, general profiling |
| Galvalume DX51D+AZ | 140 to 340 | 300 to 540 | ≥ 20 | Corrosion-prone environments, coastal roofing |
| Cold rolled SPCC | 130 to 270 | 270 to 410 | ≥ 28 | Appliance panels, interior parts, lighting |
| Structural S350GD | ≥ 350 | ≥ 420 | ≥ 16 | Structural decking, load-bearing profiles |
| High strength G550 | ≥ 550 | ≥ 560 | ≥ 10 | Purlins, framing, high-strength sections |
Prepainted Steel Coils are used across a broad range of industries because it eliminates the need for post-fabrication painting and provides a uniform coating on complex profiles. The main application areas served by YS STEEL include:
YS STEEL performs inline and laboratory testing on every master coil before shipment. The quality control plan covers substrate verification, coating thickness, color accuracy, mechanical performance, and accelerated weathering. The following tests are standard for each production lot:
Q: What is the difference between prepainted galvanized steel and prepainted galvalume steel?
A: Prepainted galvanized steel uses a zinc-coated substrate, which provides sacrificial protection at cut edges and scratches. Prepainted galvalume steel uses a coating of approximately 55% aluminum, 43.4% zinc, and 1.6% silicon, which offers better long-term corrosion resistance in most atmospheric conditions, especially in coastal and high-temperature environments. Galvalume substrates typically perform better against rust creep at exposed edges, while galvanized substrates may provide better cut-edge protection in alkaline or trapped moisture conditions. YS STEEL recommends galvalume for roofing and exterior panels where edge corrosion resistance is critical, and galvanized for applications where weldability or lower cost is the main driver.
Q: What paint system should I choose for a coastal or high-humidity environment?
A: For coastal, marine, or high-humidity environments, YS STEEL recommends either PVDF or HDP as the topcoat. PVDF has the strongest UV resistance and chemical stability because it contains a high proportion of fluoropolymer resin, making it suitable for premium facades and buildings within 500 meters of salt water. HDP delivers very good UV resistance and better cost performance for moderately corrosive environments. In addition to the paint system, the substrate is equally important: use a galvalume substrate with at least AZ150 coating mass for severe coastal exposure. The primer should be epoxy-based to create a strong barrier against moisture penetration. YS STEEL also recommends a thicker back coat on the reverse side to prevent under-film corrosion in high-humidity areas.
Q: Can YS STEEL match a custom RAL or brand color?
A: Yes, YS STEEL offers custom color matching for Prepainted Steel Coils. The customer can provide a RAL number, a PANTONE reference, or a physical color sample. The YS STEEL laboratory prepares a drawdown on the selected substrate and coating system, then measures the color with a spectrophotometer. The drawdown is sent to the customer for approval before mass production. For brand-specific colors, YS STEEL can retain the approved standard in its color archive, which allows repeat orders to be produced with minimal color variation. The standard color tolerance is ΔE ≤ 1.5 between batches, and tighter control can be agreed for large projects.
Q: What is the typical minimum order quantity and lead time for YS STEEL?
A: The minimum order quantity for standard colors and specifications is usually 25 to 50 metric tons per line item, depending on the substrate and width. For custom colors, the minimum order is typically 50 metric tons because the paint line needs a dedicated paint mixing and cleaning cycle. YS STEEL may accept smaller trial orders for existing stock coils or standard RAL colors. The normal lead time is 25 to 35 days after order confirmation and color approval. If substrate stock is available at the YS STEEL mill, production can be completed in 15 to 20 days. Shipping time depends on the destination port and selected logistics method.
Q: What tolerances can YS STEEL guarantee for thickness, width, and coating?
A: Standard dimensional tolerances are based on the substrate specification and international standards. For thickness, YS STEEL controls variations within ±0.02 mm for strip thickness from 0.12 mm to 0.40 mm, within ±0.03 mm for 0.40 mm to 0.80 mm, and within ±0.05 mm for 0.80 mm to 1.50 mm. Width tolerance is +0/-1 mm for slit coils and +0/-2 mm for mill-edge coils. Coating dry film thickness is controlled within ±2 microns of the agreed value. Color difference is maintained within ΔE ≤ 1.0 across the same coil and ΔE ≤ 1.5 between production batches. Tighter tolerances can be quoted for high-precision applications such as appliance panels and architectural facades.
