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SC604 is a borate free, high solids, low VOC single pack acrylic thin film intumescent for the protection against fire of structural steelwork.

SC604 is optimised to provide 60 minutes fire resistance to ‘I’ section beams and columns, hollow columns and beams, as well as cellular beams,
concrete filled hollows and solid rods. Limited 90 minute is also available. SC604 can be used on steel, cast iron, and galvanised steel. On-site, standard dry version, SC605, is also available.

  • Competitive loadings
  • Compatible with various primers and topcoats
  • Easy to apply
  • Fast dry
  • On-site grade, SC605, also available
  • Optifire®+ unique traceability identifier


Technical data

CertificationEN 13381-6 Protection of Concrete Filled Hollow Sections
EN 13381-8 Protection of Structural Steel
EN 13381-9 Protection of Cellular Beams
EN 13381-10 Protection of Solid Steel Rods
ETA 21/0683
CE Marking
Building ClassificationC1, C2, C3 and C4 environments only
For full details, please consult Nullifire specification guidelines.
Construction Phase6 months with topcoat once fully dried (see environmental resistance)
Volume Solids72% ±3%
VOC317 g/litre
Recommended Thickness Per CoatDFT: 720 microns - maximum
WFT: 1000 microns - maximum
Higher thicknesses may be possible, but will impact the drying times. These thicknesses are recommended for optimum film build and drying balance.
Consumption923 g/m² @ 500 μm DFT
Average Drying Times
(at 20°C)
To Touch – 30 minutes
To Recoat – 4 hours
To Handle – variable depending on conditions
These figures are given as guidance only. Other factors such as air movement, temperature and coating thickness must be considered.
Application Temperature+5°C to +35°C
StorageStore in secure, dry warehouse conditions between +0°C and +35°C
Shelf Life12 months when stored as recommended in original unopened container


SC604 is a borate free, high solids, low VOC single pack acrylic thin film intumescent for the protection against fire of structural steelwork.


Application Conditions

  • Ensure adequate through ventilation during application
  • Application temperature range 5 °C to +35 °C, relative humidity < 85% and a steel surface temperature at least 3 °C above the dew point.

Necessary Tools: Airless spray equipment is recommended and should match these guidelines:

  • Operating Pressure: Min. 3100 psi (218 kg/cm²)
  • Tip Size: 19 – 25 thou
  • Fan Angle: 20° – 40°
  • Hose Diameter: 10 mm (3/8”) (internal diameter)
  • Hose Length: Max. 30 metres.
  • Inline filters should not normally be used

Substrate Preparation
SC604 should only be used on substrates which have had all mill-scale removed and blasted to an average blast profile of 75 microns, with a minimum of 40 microns, and a cleanliness of Sa 2.5 must be achieved before application of recommended primer. All surfaces must be clean, dry and free from contamination before coating application.

Primer: For recommended primers, please consult Nullifire.

  • Nullifire has carried out compatibility testing on various primers, but have no control over primer consistency from other manufacturers.
  • The primer system shall not exceed 150 microns DFT total, with an absolute maximum allowable in overlap areas only of 200 microns DFT.
  • Primed steel surfaces that are visibly high in gloss must be abraded/sanded to a matt finish
  • The primer must be applied in accordance with the manufacturer’s instructions.
  • It is recommended that a small test patch or area is prepared with the intumescent before commencing the full application. This is to ensure that
  • no issues occur with compatibility, adhesion or drying etc.

Topcoat: For recommended topcoats, please consult the Nullifire technical team.

  • Nullifire has carried out compatibility testing on various topcoats, but have no control over the topcoat consistency from other manufacturers.
  • The type, DFT and number of layers of topcoat must be in accordance with the specification. Specifications will be driven by the Nullifire Specification Guidance or the appropriate product ETA.
  • The topcoat must be applied in accordance with the manufacturer’s instructions.
  • It is recommended as best practice that a small test patch or area be prepared before commencing the full application to ensure that there are no issues with compatibility, adhesion or drying, etc.

Mixing and Thinning
Nullifire intumescents are supplied without the need to add thinners for application, and is not recommended, However, if necessary, xylene (FC150)
may be added up to a maximum of 2%. Thinning may impact the ability of the coating to hold up at the recommended WFT. SC604 should be mechanically stirred prior to use until homogeneous

Usage Guidelines

Application Instructions: Detailed application instructions are available for SC600, SC800 and SC900 series that must be consulted prior to commencing application.

An appropriate specification must be used for the protection of the full system in accordance with the environmental classification for the environment where the building is located. The environment during construction and transport should also be considered, if necessary, and the worst case used. Nullifire can assist with selecting an appropriate specification.

Environmental Resistance
The construction phase environmental conditions may vary from those during the final building classifications. The construction phase may include
higher exposure to the environment than the final classification. Each product and specification should be considered for the resistance during this construction phase including the limitations and caveats. During the drying phase, the intumescent must be protected from all forms of water
including rain. In all cases, prolonged water contact must be avoided, including condensation, standing water, heavy running water and fresh concrete run-off (including alkaline moisture). Exposure may lead to detrimental damage to the coating system.

Protective Equipment
USE IN WELL VENTILATED CONDITIONS and ensure all recommended protective equipment is worn during handling & use of this product. For full recommendation, refer to safety data sheet.

Health + Safety Precautions

Safety data sheet must be read and understood before use. Flammable - keep away from open flames and other ignition sources.


25kg drum

Color : Off-white


Fresh intutumescent can be removed using xylene (FC150). Dried on intumescent may be removed using a paint scraper. Spray equipment must
only be cleaned using xylene (FC150).

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