Ind Pu Topcoat – Construction Guide
1. Pre-application preparation
1Substrate inspection and preparation
Check substrate cleanliness, surface roughness and temperature/humidity conditions. Blast steel to Sa 2.5 (ISO 8501-1) with a surface profile of Rz 40-75 μm. Apply the primer within 4 h after blasting. Substrate temperature ≥ dew point +3 °C, relative humidity ≤ 85 %.
2Coating preparation
Weigh the base and the hardener precisely in the single- or two-component ratio stated on the product label. Mix with a powered stirrer at low speed (300-500 rpm) for 3-5 minutes until homogeneous. Add 0-10 % of the dedicated thinner as required to reach the application viscosity. Allow to mature for 15-30 minutes at 23 °C before use.
3Environmental condition check
Application temperature: 5-40°C (substrate temperature ≥ dew point +3°C). Relative humidity: ≤85%. The application area should be well ventilated. For outdoor application, avoid rain, snow, strong wind, and direct sunlight.
2. Application process
| Application method | Parameters | Applicable scenarios |
|---|---|---|
| Airless spray | Nozzle 0.38-0.53 mm, pressure 15-25 MPa | Large steel structures, storage tanks, vessels |
| Conventional air spray | Nozzle 1.5-2.0 mm, pressure 0.3-0.5 MPa | Small/medium workpieces and equipment housings |
| Brush / roller application | — | Small-area repairs, stripe coating of welds, edge reinforcement |
Recommended dry film thickness (DFT):30-60 μm per coat. Achieving the specified film thickness may require several coats. Observe the minimum recoat interval between coats (see the TDS drying schedule).
III. Application precautions
1. If the maximum recoat interval is exceeded, the surface must be sweep-blasted (low pressure 0.2-0.3 MPa, non-metallic abrasive) to create a mechanical anchor profile.
2. Welds, free edges, bolt holes and similar areas must be stripe-coated first to ensure the coating thickness meets the specification at these vulnerable points.
3. Keep the coating continuously agitated during application to prevent pigment settling, especially for products containing heavy pigments such as zinc dust, mica iron oxide or glass flakes.
4. Two-component coatings must never be used beyond their pot life (4-8 h at 23 °C): cross-linking has already started, and further use will cause loss of adhesion and chalking of the film.
5. When applying at low temperature (<5 °C) the hardener's reactivity drops markedly; use a low-temperature curing agent or take heating measures.
6. During the curing period after application the coating must not come into contact with water (epoxy resin has limited water resistance, and amine hardeners develop amine blush / white spotting on contact with moisture).
IV. Safety and environment
1. Applicators must wear protective equipment: gas mask with A2P2 filter cartridge, safety goggles, nitrile gloves and anti-static work clothing.
2. Open flames and work generating sparks or high temperature, such as welding and cutting, are prohibited in the application area. Use explosion-proof electrical equipment.
3. Dispose of waste coating and containers as HW12-class hazardous waste in accordance with the National Catalogue of Hazardous Wastes.
4. Do not pour leftover coating into drains or onto the ground. Collect it and hand it over to a licensed hazardous-waste disposal contractor.
V. Quality inspection
| Inspection items | Method | Acceptance criteria |
|---|---|---|
| Surface preparation | ISO 8503 surface roughness comparator | Sa2.5, Rz 40-75μm |
| Dry film thickness (DFT) | ISO 2808 electromagnetic induction method | 80 % of readings ≥ specified value, no reading below 80 % of the specified value |
| Adhesion | ISO 4624 pull-off test / ISO 2409 cross-cut test | ≥≥3-5 MPa |
| Pinholes/holidays (discontinuities) | High-voltage holiday (spark) testing | No pinholes/holidays (coating discontinuities) |
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