1.What are the specific requirements for primer?
Adhesion foundation: Form chemical bonds with metal substrates (such as galvanized layers) to ensure that the coating system does not fall off;
Anti-rust barrier: Isolate water vapor and oxygen from contact with metals, delaying electrochemical corrosion.
2.How to choose primer construction process parameters?
Viscosity control: 20-30s (apply - 4 cups, 25℃), ensure good leveling when roller coating to avoid orange peel texture;
Dry film thickness: 5-10μm, too thin will affect rust prevention, too thick will easily lead to incomplete drying;
Curing conditions: 180-220℃ hot air drying for 5-10 minutes, and the degree of curing needs to be tested (infrared spectroscopy ≥95%).
3.What are the specific requirements for topcoat?
Weather protection: resist environmental erosion such as ultraviolet rays, acid rain, salt spray, etc., and extend service life; • Decoration and function: provide color and glossiness, while meeting special requirements such as fingerprint resistance and scratch resistance.
4.How to choose the construction process parameters of topcoat?
Viscosity control: 25-35s (apply - 4 cups, 25℃), high viscosity ensures thick film coating (15-20μm dry film);
Surface effect control: Matt surface: add silica matting agent (particle size 1-3μm), gloss 60°≤30%;
Metallic paint surface: add aluminum powder (particle size 5-15μm), the directional arrangement rate must be controlled to be ≥85% to ensure the metallic texture;
Curing conditions: high temperature drying at 200-240℃ for 8-15 minutes, and the peak curing temperature must be confirmed by differential scanning calorimetry (DSC) to be ≥180℃.
5.What are the matching principles of primer and topcoat?
Chemical compatibility
Resin system matching: For example, epoxy primers need to be matched with epoxy or polyurethane topcoats, and polyester primers and PVDF topcoats should not be directly matched (polarity difference leads to decreased adhesion);
Curing mechanism matching: Thermosetting primers (such as epoxy) need to be matched with the same type of thermosetting topcoats, and thermoplastic topcoats (such as PVC) should not be mixed with thermosetting primers.
Thickness matching
Primer thickness: Topcoat thickness ≈ 1:3 (such as primer 8μm + topcoat 24μm), to ensure stress balance in the coating system and avoid cracking;
The topcoat thickness needs to be increased to 25-30μm in coastal areas, and the primer thickness needs to be ≥10μm in industrial acid rain areas. Functional synergy • Anti-corrosion scenario: epoxy primer (rust-proof) + fluorocarbon topcoat (weather-resistant), forming "rust-proof + weather-resistant" double protection;
Home appliance scenario: polyester primer (adhesion) + high-gloss polyester topcoat (decorative), while adding antistatic additives (surface resistance 10⁶-10⁹Ω).