1、Substrate Pretreatment

● Degreasing 

By alkaline solution or electrolytic cleaning, completely remove the oil on the surface of the steel plate (residual oil ≤50mg/m²) to ensure the adhesion of the coating.

● Phosphating Treatment

Compact phosphate conversion film (film weight 1.5-3.0g/m²) for enhanced rust protection (according to ISO 9717)

● Passivation

Some processes increase the chromate passivation layer (Cr³ + 10mg/m² content) for improved corrosion resistance

2、Multi-layer Coating

● Primer

Epoxy based coating, thickness 5-10μm, provides substrate rust protection and adhesion (scratch test Class 0, ASTM D3359)

● Topcoat

Polyester, silicone modified polyester or fluorocarbon resin, thickness 5-45μm, color and weather resistance (QUV 2000 hours light retention ≥80%)

● Back Paint

Epoxy or acrylic coating, thickness 5-15μm, protects the back of the steel plate from environmental erosion.

3、High-temperature Curing

● The coating is cured for 20-30 seconds in a continuous baking oven at 200-240℃ to form a cross-linked network structure (pencil hardness ≥H, ASTM D3363).