Precautions for Steel Structure Anti-corrosion Works
Edit by:Ellermann Steel
Anti-corrosion coating is a critical process in ensuring the long-term stability and durability of steel structures. To ensure the quality of coating, strict adherence to operational standards is necessary. Below are the key precautions for steel structure anti-corrosion works.
1. Preparation
- Material Selection:The selection of anti-corrosion materials must meet design specifications. Commonly used materials include primers, topcoats, and thinners. Primers typically used are red lead oil-based rustproof paint and molybdenum-chromium red epoxy rustproof paint; topcoats include various colors of alkyd magnetic paint and alkyd blended paint. All materials should meet relevant technical standards and come with the manufacturer's certificate of conformity.
- Main Equipment:Required equipment includes sandblasting guns, air pumps, recovery devices, spray guns, spray paint air pumps, hoses, scrapers, hand grinders, sandpaper, wire brushes, cotton wire, small compressors, paint buckets, brushes, acid washing tanks, and accessories.
- Operating Conditions:Painters must hold a specialized operator certificate. Anti-corrosion works should only proceed once the steel structure has passed inspection and meets design requirements. Work areas should have proper fire protection and ventilation measures to prevent fire and poisoning risks. Outdoor anti-corrosion works should be scheduled in suitable weather conditions, avoiding strong winds, rain, and extreme cold.
2. Operation Process
1>.Process Flow:Surface cleaning → Primer application → Topcoat application → Inspection and acceptance.
2>.Surface Cleaning:Coating works should begin only after the steel structure has passed installation inspection. Prior to painting, all rust, weld slag, welding spatters, oil stains, and dust must be cleaned off. The quality of surface cleaning directly impacts the adhesion and performance of the coating. Surface cleaning is classified into two levels:
- Level 1: Steel surface reveals metallic color, cleaned by sandblasting, shot peening, or acid washing.
- Level 2: The steel surface retains clean mill scale, cleaned by wire brushes or sandpaper.
3>. Primer Application:The primer should be thoroughly mixed to ensure consistent color and viscosity. When applying the first coat, brush strokes should be uniform, and seams must be neat. Brushes should be frequently dipped and used with short strokes to avoid excess paint and dripping. After the first coat, ensure a proper drying time before applying the second coat to avoid wrinkling or dripping.4>. Topcoat Application:
After applying the primer, the steel structure should be assembled and cleaned before topcoat application to remove welding slag and touch up any damaged areas. The topcoat should be mixed to ensure uniform color and consistency, and the application method is similar to the primer. During spray coating, adjust the nozzle size, spray pressure, and hose length to ensure the spray angle is perpendicular to the surface.
5>. Coating Inspection and Acceptance:
After the coating is completed, protect the surfaces to prevent contamination from dust or debris. The coating should have consistent color, a bright finish, and be free of wrinkles or bubbles. The thickness of the coating should be measured with a coating thickness gauge, and the average value should be taken from three measurement points.
3. Quality Standards
1>. Material Quality:
The coatings, thinners, and hardeners must meet design and relevant standards. Prior to coating, the steel surface must meet rust removal requirements and be free of weld slag, rust, dust, and oil stains.
2>. Appearance Quality:
The coating should be uniform, with consistent color, good adhesion, and no visible wrinkles, bubbles, or drips. For touch-up coats, the film should be intact and well-adhered.
3>. Coating Thickness:
Coating thickness should comply with the "Steel Structure Construction and Acceptance Specifications." Thickness is measured using a coating thickness gauge, with an average of three measurements taken at different points.
4. Protection of Finished Products
1>. Temporary Protection:
Steel components should be temporarily enclosed to prevent foot traffic and damage to the coating.
2>. Prevent Contamination:
If there are strong winds or rain within 4 hours after coating, the components should be covered to protect against dust and moisture, which could affect adhesion.
3>. Transportation Protection:
During transportation, care should be taken to avoid bumping, scraping, or dragging the components on the ground, which could damage the coating. Components should not come into contact with acidic liquids to prevent corrosion.
5. Common Quality Issues to Note
1>.Temperature Requirements:Coating works should be conducted within a temperature range of 5–38°C. If the temperature is below 5°C, low-temperature coatings should be used. Work should stop if the temperature exceeds 40°C to prevent the formation of bubbles and poor adhesion.2>.Humidity Requirements:Coating works should not be performed if the air humidity exceeds 85% or if condensation is present on the steel surface.3>.Pre-treatment of Hidden Areas:Before fabricating the steel structure, areas that are difficult to clean or hidden from view, such as structural gaps, should be pre-cleaned and pre-coated.
Steel structure anti-corrosion works are critical to extending the lifespan and ensuring the safety of structures. By following strict material selection, operational processes, and quality control standards, the quality of anti-corrosion coatings can be ensured, contributing to the overall longevity and reliability of the project.
