Container House Painting Methods

Container house painting methods mainly include substrate treatment, coating selection, spraying process, and paint film inspection, among other steps. A detailed process flow needs to be formulated based on the type of container, the usage environment, and anti-corrosion requirements.

1. Substrate Treatment

Substrate treatment is the foundation of painting quality, and it is necessary to ensure that the steel surface is clean and free of impurities.

• Panel Treatment: Select Grade A panels as specified in ISO8501, remove oil, dust, corrosion products, etc., and dry them by wiping with a solvent or air blowing.
• Profile Treatment: Use an 8-nozzle sandblasting machine for treatment. The abrasive ratio is S280:G25:Steel wire segments = 5:3:2, with a linear speed of 3 m/min. The sandblasting grade, roughness, and cleanliness must meet the standards.
• Secondary Sandblasting: After container assembly, perform secondary sandblasting on welds and other areas to remove oxides and splashes, release stress, and prevent corrosion of the weld areas.

2. Coating Selection and Ratio

Select an appropriate coating system based on the usage environment and strictly follow the specified ratios.

• Exterior Surface: Usually, a three-layer coating system is adopted, with epoxy zinc-rich primer as the base coat, epoxy intermediate coat as the middle layer, and acrylic topcoat, chlorinated rubber paint, polyurethane topcoat, or fluorocarbon paint as the finish.
• Interior Surface: A two-layer coating system is used, with epoxy zinc-rich primer as the base coat and epoxy topcoat as the finish, which must meet food hygiene and safety requirements.
• Underframe: Epoxy zinc-rich primer is used as the base coat, and modified epoxy underframe paint or asphalt paint can be selected as the finish.
• Thinner and Ratio: Select a thinner according to the type of coating, such as acrylic polyurethane thinner. The dilution amount should be controlled within 0-5% (airless spraying), 0-10% (air spraying), or 0-3% (roller coating/brush coating).

3. Spraying Process

The spraying process directly affects the quality of the paint film, and an appropriate method should be selected based on the type of coating and construction conditions.

• Airless Spraying: Suitable for high-solid coatings, with a rated paint heating temperature of about 50℃, which can produce a smooth and full paint film. The nozzle diameter is 0.2-0.4 mm, and the spraying pressure is 15-20 Mpa.
• Air Spraying: The nozzle diameter is 2.0-2.5 mm, and the air pressure is 0.3-0.4 Mpa, suitable for scenarios with low requirements for paint film thickness.
• Roller Coating/Brush Coating: Suitable for local repairs or complex structural areas, such as dead corners and welds of the container body. Brush coating requires a 2.5-inch wide bent-handle paintbrush, which is flexible to operate and has strong penetration.

4. Paint Film Inspection and Quality Control

After spraying is completed, paint film inspection is required to ensure compliance with standards.

• Thickness Inspection: Use a dry/wet film thickness gauge to inspect the paint film thickness and ensure it meets the requirements of the coating specification sheet.
• Adhesion Inspection: Inspect the paint film adhesion through a cross-cut test to ensure it reaches Grade 0 standard.
• Appearance Inspection: Check whether the paint film is flat and smooth, without defects such as sagging, pinholes, or orange peel.