1. Pickling & Passivation
Core effect: Removes hot-rolled oxide scale, surface rust and oil stains; forms a thin passive film on the steel surface to inhibit initial oxidation during storage/transportation.
Process: Acid pickling (sulfuric/hydrochloric acid) → water washing → neutralization → passivation (chromate/non-chromate solution) → drying.
Application: Pre-treatment for subsequent processing (slitting, forming, coating); suitable for coils to be fabricated into panels, cladding and structural parts, ensuring a clean base surface for uniform patina formation.
2. Pre-Weathering Treatment (Controlled Oxidation)
Core effect: Factory-induced controlled outdoor/accelerated oxidation to form a preliminary dense, uniform patina on the coil surface; eliminates on-site rust powder shedding and shortens the outdoor patina maturation period from 12–24 months to 1–3 months.
Process: Simulated outdoor humidity/temperature exposure → surface adjustment → natural oxidation to form a stable base patina → surface sealing (optional).
Application: Coils for architectural decorative products (facades, signboards, sculptures); ideal for projects requiring immediate uniform rust aesthetics without initial staining.
3. Transparent Weathering Sealer Coating
Core effect: Applies a thin, breathable transparent polymer sealer (water-based/solvent-based) to the coil surface; traps loose rust powder in the initial oxidation stage, accelerates patina uniformity and does not block natural patina growth.
Process: Surface cleaning → roller coating of sealer (thickness: 5–20 μm) → low-temperature curing (80–120℃).
Application: Coils for building cladding, curtain walls and outdoor furniture; prevents rust powder staining of adjacent materials and maintains the original steel texture.
4. Shot Blasting/Sand Blasting
Core effect: Removes scale, rust and surface burrs via high-speed abrasive impact; creates a uniform matte/rough metallic surface texture and improves the adhesion of subsequent coatings (if applied).
Process: Dry shot/sand blasting → dust removal → surface cleaning.
Application: Coils for custom fabrication (sculptures, landscape structures) or coils to be coated with anti-corrosion primers; the rough surface enhances mechanical bonding with coatings or concrete.
5. Oil Coating (Anti-Rust Oil)
Core effect: Applies a thin film of volatile/non-volatile anti-rust oil to the coil surface; forms a physical barrier to isolate air and moisture, preventing rust during long-term storage (6–12 months) and sea transportation.
Process: Surface degreasing → roller coating of anti-rust oil (thin film) → winding and packaging.
Application: Unprocessed coils for long-term inventory or international shipping; the oil layer can be easily removed by degreasing before subsequent fabrication/installation.
6. Slit Edge Treatment
Core effect: Targeted treatment for coil slitting edges (sharp, unprocessed edges prone to micro-corrosion); eliminates edge burrs and forms a protective layer to prevent initial edge rusting.
Process: Edge deburring → edge passivation/light coating of sealer → drying.
Application: Slitted coils for panel/trim fabrication; a matching auxiliary treatment for full-surface treated coils to ensure overall corrosion resistance.
7. Electrostatic Powder Coating (Optional Functional Coating)
Core effect: Applies a colored/transparent powder coating to the coil surface for enhanced corrosion resistance in harsh environments (high salt spray, industrial acid mist); the coating is wear-resistant and scratch-proof.
Process: Surface pre-treatment (pickling/shot blasting) → electrostatic powder spraying → high-temperature curing (180–200℃).
Note: Blocks natural patina formation; only for projects prioritizing corrosion resistance over the inherent weathering steel rust aesthetic.
