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What is Matt Color-coated Steel
Matt Color-coated Steel refers to pre-painted steel coil or sheet that has a low-gloss, non-reflective finish on its surface.
Why is it so outstanding?
Production Processes
- Ordinary color-coated steel and textured color-coated steel share similar basic production processes:
Uncoiling → Seaming → Degreasing → Chemical Pretreatment → Primer Coating → Primer Baking
→ Primer Cooling → Top Coating → Top Baking → Top Cooling → Inspection → Slitting → Recoiling.
However, the key difference in embossed color-coated steel lies in the topcoat (finish coat) stage.
- Ordinary color-coated steel: During the topcoat process, the coating is uniformly applied to the pretreated substrate and then cured through baking to form a smooth paint film.
- Matt surface color coated steel: To achieve the embossed effect, special coating formulations and/or application processes are typically used during the topcoat stage.
- Special coating formulation: May contain certain additives that, during baking and curing, cause the coating surface to undergo micro-shrinkage or uneven flow, thereby producing the embossed pattern effect.
- Special coating process: This may involve controlling coating thickness, designing the coating roller with special features, or precisely controlling baking conditions (such as temperature and airflow) to induce the coating to form the desired grid structure during curing. Some patents mention controlling grid patterns by monitoring wet film thickness and coating consumption.
Are you also curious about its layer structure and materials?
1. General Structure of the Coating System (From Inner to Outer Layers)
The typical coating structure of color-coated steel sheets generally includes the following layers:
-
SUBSTRATE:
This is not the coating itself, but it serves as the foundation for the coating to adhere to.
Materials: Primarily stainless steel, galvanized steel sheets (GI/HDG - Hot-Dip Galvanized), galvanized aluminum-zinc steel sheets (GL/Galvalume/Aluzinc), and aluminum-coated steel sheets (Aluminized Steel), etc. Among these, galvanized and galvanized aluminum-zinc are the most common substrates, as they provide excellent corrosion protection.
-
PRE-TREATMENT LAYER (PRE-TREATMENT LAYER / CHEMICAL CONVERSION COATING)
Located between the metal substrate and the primer.
Function: Enhances adhesion between the coating and the substrate and further improves the substrate's corrosion resistance.
Materials: Common types include chromate treatment and chrome-free treatments (such as silane treatment and titanium zirconium salt treatment). With increasing environmental protection requirements, chrome-free treatment is becoming increasingly widespread.
-
PRIMER COAT
Applied over the pre-treatment layer.
Function: Primarily enhances adhesion between the topcoat and the pre-treatment layer and provides additional corrosion protection. It is a critical component of the coating system, playing a key role in the corrosion resistance and durability of the color-coated sheet.
Materials:
Epoxy Resin: A common primer material with excellent adhesion and corrosion resistance.
Polyurethane: Offers good flexibility and abrasion resistance.
Polyester: Can also be used as a primer.
Thickness: Typically thin, generally between 5–20 microns (µm).
- TOP COAT/FINISH COAT
Applied over the primer layer, it is the outermost layer of the color-coated sheet and is directly exposed to the external environment.
Function: Provides color, gloss, texture, and primary weather resistance, corrosion resistance, UV resistance, and wear resistance. The visual appearance and most performance characteristics of color-coated sheets are determined by the topcoat.
Material Classification (primarily categorized by resin type):
| TYPE | FEATURES | APPLICATIONS |
|---|---|---|
| Polyester (PE) | Cost-effective, wide color options, good adhesion, and excellent processing | Most common topcoat for color-coated steel sheets; widely used in construction, home appliances, etc. |
| Silicon-modified Polyester (SMP) | Enhanced hardness, weather resistance, gloss retention, and anti-chalking with silicon resin | Building roofs, walls, and other applications requiring higher durability |
| Polyvinylidene Fluoride (PVDF) | Exceptional weather, UV, chemical resistance, long lifespan, self-cleaning, fade, and chalking resistance | High-rise buildings, curtain walls, airports, power plants, extreme climates, and high durability needs |
| High-Durability Polyester (HDP) | Improved weather resistance and durability over standard PE; lower cost than PVDF | Mid-to-high-end applications requiring better durability than PE but lower cost than PVDF |
| Polyurethane (PU) | Excellent abrasion resistance, toughness, chemical resistance, and good gloss retention | Applications requiring high abrasion and impact resistance, such as door panels and garage doors |
| Acrylic | Vibrant colors, high gloss, but inferior weather resistance to polyester | Indoor decoration, home appliances, and areas with high aesthetic demands but less harsh environments |
| Plastisol | Thick coating, superb abrasion and chemical resistance, textured surface possible | Applications needing thick coatings and abrasion resistance: grain silos, pipelines, some roof surfaces |
| Special Topcoats | Special functions: self-cleaning, thermal insulation, antibacterial, anti-static | Achieved by adding special materials to base resins or using specialized processes |
- Back Coat (Backing Coat)
Applied to the back of the steel sheet, typically on the opposite side of the substrate.
Function: Provides corrosion protection for the back side and prevents scratches on the back side. It may also have an aesthetic function (e.g., white back coat).
Material: Typically polyester, epoxy resin, or other simplified formulations, with a thickness generally thinner than the topcoat, such as 5–10 microns.
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