01

Impact of Temperature on Coating Performance:

Analyzing Differences with Data, Solving Problems with Solutions

At 10°C, the drying speed and curing strength of steel structure fireproof coatings undergo significant changes, directly affecting fire resistance and durability. According to the performance test requirements in Appendix C of "GB 14907-2018 Steel Structure Fireproof Coatings", comparing the performance differences between 23°C (standard application temperature) and 10°C:

• Drying Time: At 23°C, the surface dry time for thin-film fireproof coatings is ≤4 hours, and the hard dry time is ≤24 hours. However, in a 10°C environment, the surface dry time can extend to 6-8 hours, and the hard dry time may even exceed 36 hours, an increase of over 50%. If the application rhythm is not adjusted promptly, subsequent spray layers might be applied before the previous layer is fully dry, leading to wrinkling or peeling.

  
  

• Bond Strength: At 23°C, the bond strength of thick-film fireproof coatings is ≥0.05 MPa. At 10°C without measures, it may drop below 0.03 MPa, failing to meet national standards and making the coating prone to cracking under vibration or temperature changes later.

  
  

Solutions:

• Material Adjustment: Select fireproof coatings labeled as "Low Temperature Applicable" or, following the coating instructions, add a dedicated low-temperature curing agent at 10°C (dosage must be strictly controlled at 3%-5% of the total coating weight; excess can make the coating brittle).

  
  

• Process Optimization: Reduce the thickness of each spray pass by 20% compared to 23°C (e.g., for thin-film coatings, reduce from 0.5mm per pass to 0.4mm). Extend the interval between passes to 48 hours, ensuring the previous layer is completely dry before the next application.

  
  

• Auxiliary Heating: If conditions allow, use portable hot air blowers (temperature controlled at 40-50°C, distance from coating ≥50cm) for intermittent heating of the application surface. Heat 3-4 times daily, for 30 minutes each time, to accelerate moisture evaporation.

  
  

02

Strict Control of the Application Environment:

Compliance with Standards ≠ Safety, Multi-Parameter Collaborative Management

"GB 50205-2020 Standard for Acceptance of Construction Quality of Steel Structure Engineering"明确规定，the application environment temperature for steel structure fireproof coatings should be between 5-45°C. While 10°C is within the compliant range, vigilance is needed against the issue of "temperature meeting standards but other parameters exceeding limits." Measured data shows:

• Humidity Impact: When ambient humidity is >85%, even at 10°C, moisture in the coating struggles to evaporate. The hard dry time of the coating will extend by another 30%, and issues like moisture regain and mold growth are likely later.

  
  

• Ventilation Conditions: When applying in enclosed spaces (e.g., inside workshops), at 10°C, slow air circulation can cause the concentration of volatilized coating solvents to rise to 1.5 times that at 23°C. This not only affects applicator health but can also cause an "orange peel" texture on the coating surface.

  
  

Solutions:

• Real-time Monitoring: Record temperature and humidity every 2 hours during application using a hygrometer (accuracy ±0.5°C, ±5% RH). If humidity >85%, immediately activate dehumidifiers (configure 1 unit with a dehumidification capacity ≥20L/day per 100㎡ space). Resume work only after humidity drops below 80%.

  
  

• Ventilation Control: Install axial flow fans in enclosed spaces (wind speed controlled at 1-2 m/s) to create air convection. Simultaneously, use VOCs detectors to ensure solvent concentrations remain below national standard limits (Benzene ≤0.1mg/m³, Toluene + Xylene ≤1.0mg/m³).

  
  

• Rain/Snow Protection: Check the weather forecast before application. If rain or snow is expected within 6 hours, set up temporary rain shelters (maintaining temperature inside the shelter at 10-15°C) to prevent the coating from freezing (a sudden temperature drop below 5°C can cause internal ice formation, leading to honeycomb-like pores upon thawing).

  
  

03

Key Points of Application Technique:

Low-Temperature Standards from Surface Prep to Spraying

At 10°C, the meticulous control of application techniques directly determines coating quality. First is surface preparation, an easily overlooked "invisible threshold":

• Derusting Standard: According to "GB/T 8923.1-2019 Preparation of steel substrates before application of paints and related products", the derusting grade for steel surfaces must reach Sa2.5 level (steel surface free from visible oil, grease, dirt, mill scale, rust, etc.; only minimal staining in the form of faint spots or streaks is permissible). If derusting is incomplete, the adhesion between the coating and the substrate at 10°C can decrease by an additional 15%.

  
  

• Primer/Bonding Agent Application: When applying the primer/bonding agent, control the application thickness to 0.1-0.2mm. The drying time at 23°C is 1-2 hours, but needs to be extended to 3-4 hours at 10°C. Furthermore, the first coat of fireproof coating must be sprayed within 4 hours after primer application to prevent the primer from absorbing moisture and losing effectiveness.

  
  

Parameter adjustments during the spraying operation are equally critical:

• Spray Gun Parameters: Maintain air pressure at 0.4-0.6 MPa (increase by 0.1 MPa compared to 23°C). Select a nozzle diameter of 2.5-3.0 mm (commonly 2.0-2.5 mm at 23°C) to ensure even atomization of the coating.

  
  

• Spray Distance: Control the distance between the spray gun and the steel surface to 30-40 cm (25-30 cm at 23°C). Slow the movement speed to 30-40 cm/s (40-50 cm/s at 23°C) to avoid sagging caused by poor adhesion before the coating sets.

  
  

04

Coating Storage and Usage:

Specifics of Low-Temperature Storage, "Time Control" After Opening is Key

At 10°C, the storage life and pot life of coatings shorten. Improper management can lead to the entire batch of coating being scrapped. According to the storage requirements in "GB 14907-2018":

• Storage Temperature: Coatings should be stored in a cool, dry place at 5-35°C. When storing at 10°C, keep them away from doors and windows (avoiding temperature fluctuations exceeding ±3°C per day). Stack height should not exceed 3 layers (can stack 4 layers at 23°C) to prevent compaction and caking at the bottom.

  
  

• Pot Life After Opening: Once a single container is opened, it should be used within 8 hours at 23°C. At 10°C, due to slower evaporation, this can be extended to 12 hours, but the coating must be stirred every 2 hours (stirring speed 300 rpm, for 5 minutes each time) to prevent pigment settling.

  
  

• Handling Leftover Coating: Unused coating must be sealed immediately (use double sealing with a sealing strip and plastic wrap). Mark the opening time on the container. Sealed storage at 10°C should not exceed 24 hours. Before reuse, check the viscosity (should be 50-80 seconds, measured using a Ford viscosity cup #4). If viscosity is out of spec, add dedicated thinner (amount ≤3%).

  
  

Conclusion: For steel structure fireproof coating spraying around 10°C, it's essential not only to adhere to the national standard baseline of "5-45°C" but also to go the extra mile in performance adjustment, environmental control, technical details, and storage management. Precise control of every data point and thorough implementation of each solution are crucial for ensuring the steel structure can "withstand the test" in a fire. Bookmark this article to avoid pitfalls in low-temperature application!

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