Container House Painting Process

The container house painting process mainly includes steps such as paint selection, substrate treatment, painting methods, special treatments, and quality inspection.

1. Paint Selection and Specifications Select appropriate paints based on the operating environment of the container (e.g., outdoors, by the sea). For ordinary environments, epoxy resin or polyurethane paints can be used; for areas with severe salt spray corrosion, such as by the sea, heavy-duty anti-corrosion paints should be upgraded to, such as water-based high-chlorination paints or specialized powder paints. Paint specifications should clearly define parameters such as dry/wet film thickness, dilution ratio, and drying conditions. For example, epoxy zinc-rich primer requires strict control of the uniformity of zinc powder content to prevent sedimentation.

2. Substrate Treatment The steel surface should meet the Grade A standard specified in ISO 8501. Oil, rust, and oxide layers should be removed through sandblasting, with the abrasive ratio (e.g., S280:G25:steel wire segments = 5:3:2) and sandblasting grade meeting requirements. Secondary sandblasting targets areas such as welds to remove oxides and splashes generated during welding, preventing concentrated corrosion.

3. Painting Methods

   • Airless Spraying: A mainstream technique that atomizes paint through high-pressure fluid without relying on compressed air, suitable for high-viscosity materials. The spraying distance (e.g., 30-50 cm), paint temperature (about 50°C), and pump pressure should be controlled to obtain a smooth paint film.
   • Pre-spraying and Brushing: For areas such as welds and dead corners that are difficult to cover with airless spraying, pre-spraying or brushing (using a 2.5-inch bent-handle paintbrush) should be used for touch-up to ensure complete coating.
   • Powder Spraying: An environmentally friendly process that involves electrostatic adsorption of powder paint followed by high-temperature curing (180-200°C), suitable for components such as enclosed doors. The quality of pre-treatment (e.g., sandblasting grade) and coating thickness (60-80 μm) should be strictly controlled.

4. Special Treatments

   • Stirring of Zinc-Rich Paint: Two-component zinc-rich paint should be stirred continuously throughout the process to prevent zinc powder sedimentation.
   • Compatibility of Structural Sealant: Water-based paints require the addition of gemini-type organosilicon leveling agents (e.g., Hyperlev F39) to solve the problem of sealant substrate wetting.
   • Refurbishment Topcoat: Single-component acrylic paint simplifies the construction process, supports spraying, rolling, or brushing, dries quickly at room temperature (surface drying ≤ 30 minutes), and is suitable for refurbishing old containers.

5. Quality Inspection The coating should pass tests for corrosion resistance (salt spray test ≥ 500 hours), mechanical properties (adhesion reaching Grade 0), and weather resistance (aging test), meeting the standards of IICL or KTA laboratories. Food-grade containers should also pass FDA certification.