1.How should the substrate be pretreated?
Degreasing and Cleaning: Using alkaline or neutral cleaning agents, thoroughly remove grease, dust, stamping oil, and other contaminants from the steel plate surface through spraying or immersion.
Water Washing: Use multi-stage water spraying to remove residual cleaning agents and impurities.
Chemical Conversion Coating Treatment (Surface Passivation):
Purpose: To form a dense, strongly adhering non-metallic crystalline film on a clean metal surface, significantly improving corrosion resistance and coating adhesion.
Main Types:
Chromate Treatment: Traditional and efficient, but contains hexavalent chromium, subject to strict environmental restrictions, and has been gradually replaced.
Chromium-Free Treatment: Current mainstream, environmentally friendly. Includes:
Zirconium/Titanium-based Treatment: Utilizes oxides of metals such as zirconium and titanium to form a conversion film.
Silane Treatment: Organic-inorganic hybrid technology, excellent adhesion.
Composite Oxide Treatment: A composite system of multiple chromium-free metal salts.
2.How to perform painting treatment?
Primer:
A primer is applied over the conversion coating. Its main functions are corrosion protection and enhancing the adhesion of the topcoat.
Primer types: Epoxy resin, polyester resin, polyurethane, etc., typically containing rust-inhibiting pigments (such as zinc phosphate).
Topcoat:
Applied as the outermost layer, providing final color, gloss, weather resistance, and specific physicochemical properties (such as scratch resistance and acid/alkali resistance).
Topcoat types vary, with different properties:
Polyester: General-purpose, cost-effective, and with good weather resistance.
Silicone-modified polyester: Better weather resistance and durability than standard polyester, suitable for building exteriors.
High-durability polyester/fluorocarbon: Excellent outdoor weather resistance, strong color and gloss retention.
Polyvinylidene fluoride (PVDF): A recognized ultra-high weather resistance coating, mainly used in harsh environments such as high-end buildings and airports.
Plastic sol: Thick coating, good feel, strong corrosion resistance and scratch resistance, commonly used in household appliances and industrial plants.
3.How to perform post-processing and special processing?
Lamination/Coating:
Protective Film Application: Covering the coated surface with a peelable plastic film to prevent scratches during transportation and processing.
Lamination: Bonding PVC, PET, or other plastic films, or wood grain/stone grain decorative films, to the color-coated steel sheet using adhesives to achieve special decorative effects and textures (such as imitation wood grain color-coated steel sheets).
Embossing: Imprinting with patterned rollers while the coating is not fully cooled to create textures such as leather or orange peel, combining aesthetic appeal with the ability to cover minor scratches.
Printing: Using digital printing and other technologies, printing complex patterns or personalized images onto the color-coated steel sheet.
4.What does the process include?
Substrate → Degreasing → Washing → Chemical Conversion → Drying/Cooling → Primer Coating → Baking and Curing → Cooling → Topcoat Coating → Baking and Curing → Cooling → Post-treatment (Lamination/Embossing, etc.) → Rolling/Shearing
5.How to choose the surface treatment method for different applications?
For general building roofs/walls: Polyester or silicone-modified polyester can be used, with standard pretreatment.
For buildings in coastal or highly polluted industrial areas: High-weather-resistant polyester or PVDF coatings are recommended, ensuring chromium-free pretreatment quality.
For appliance casings: High-gloss, fingerprint-resistant polyester or plastisol coatings are commonly used.
For applications requiring high decorative appeal: Laminated (wood grain, stone grain) or embossed products are available.